Hifitime

+ Galileo System Time and BeiDou Time are now supported, huge thanks to [gwbres](https://github.com/gwbres) for all that work!
+ Significant speed improvement in the initialization of Epochs from their Gregorian representation, thanks [conradludgate](https://github.com/conradludgate) for [#160](https://github.com/nyx-space/hifitime/pull/160).
+ Epoch and Duration now have a `min` and `max` function which respectively returns a copy of the epoch/duration that is the smallest or the largest between `self` and `other`, cf. [164](https://github.com/nyx-space/hifitime/issues/164).
+ [Python] Duration and Epochs now support the operators `>`, `>=`, `<`, `<=`, `==`, and `!=`. Epoch now supports `init_from_gregorian` with a time scape, like in Rust. Epochs can also be subtracted from one another using the `timedelta` function, cf. [162](https://github.com/nyx-space/hifitime/issues/162).
+ TimeSeries can now be formatted in different time scales, cf. [163](https://github.com/nyx-space/hifitime/issues/163)

What's Changed
* optimise gregorian by conradludgate in https://github.com/nyx-space/hifitime/pull/160
* Remove redundant tests by SUPERCILEX in https://github.com/nyx-space/hifitime/pull/161
* Usability enhancements, especially for Python by ChristopherRabotin in https://github.com/nyx-space/hifitime/pull/165
* introducing GNSS timescales by gwbres in https://github.com/nyx-space/hifitime/pull/166

New Contributors
* conradludgate made their first contribution in https://github.com/nyx-space/hifitime/pull/160
* SUPERCILEX made their first contribution in https://github.com/nyx-space/hifitime/pull/161
* gwbres made their first contribution in https://github.com/nyx-space/hifitime/pull/166

**Full Changelog**: https://github.com/nyx-space/hifitime/compare/3.5.0...3.6.0

+ Epoch now store the time scale that they were defined in: this allows durations to be added in their respective time scales. For example, adding 36 hours to 1971-12-31 at noon when the Epoch is initialized in UTC will lead to a different epoch than adding that same duration to an epoch initialized at the same time in TAI (because the first leap second announced by IERS was on 1972-01-01), cf. the `test_add_durations_over_leap_seconds` test.
+ RFC3339 and ISO8601 fully supported for initialization of an Epoch, including the offset, e.g. `Epoch::from_str("1994-11-05T08:15:30-05:00")`, cf. [73](https://github.com/nyx-space/hifitime/issues/73).
+ Python package available on PyPI! To build the Python package, you must first install `maturin` and then build with the `python` feature flag. For example, `maturin develop -F python && python` will build the Python package in debug mode and start a new shell where the package can be imported.
+ Fix bug when printing Duration::MIN (or any duration whose centuries are minimizing the number of centuries).
+ TimeSeries can now be formatted
+ Epoch can now be `ceil`-ed, `floor`-ed, and `round`-ed according to the time scale they were initialized in, cf. [145](https://github.com/nyx-space/hifitime/issues/145).
+ Epoch can now be initialized from Gregorian when specifying the time system: `from_gregorian`, `from_gregorian_hms`, `from_gregorian_at_noon`, `from_gregorian_at_midnight`.
+ Fix bug in Duration when performing operations on durations very close to `Duration::MIN` (i.e. minus thirty-two centuries).
+ Duration parsing now supports multiple units in a string and does not use regular expressions. THis allows it to work with `no-std`.
+ Epoch parsing no longer requires `regex`.
+ Functions are not more idiomatic: all of the `as_*` functions become `to_*` and `in_*` also becomes `to_*`, cf. [155](https://github.com/nyx-space/hifitime/issues/155).

What's Changed
* Usability enhancements and python package by ChristopherRabotin in https://github.com/nyx-space/hifitime/pull/144
* Add {ceil, floor, round}_in_timesystem by ChristopherRabotin in https://github.com/nyx-space/hifitime/pull/146
* Workflow improvements by ChristopherRabotin in https://github.com/nyx-space/hifitime/pull/148
* RFC3339 and Epoch store the initial time scale used by ChristopherRabotin in https://github.com/nyx-space/hifitime/pull/149
* Use lexical_core for parsing durations by ChristopherRabotin in https://github.com/nyx-space/hifitime/pull/152
* Remove Regex in favor of lexical_core for parsing by ChristopherRabotin in https://github.com/nyx-space/hifitime/pull/153
* Fix formatting of Epochs by ChristopherRabotin in https://github.com/nyx-space/hifitime/pull/156
* Methods renamed to be idiomatic by ChristopherRabotin in https://github.com/nyx-space/hifitime/pull/157


**Full Changelog**: https://github.com/nyx-space/hifitime/compare/3.4.0...3.5.0

What's Changed
* Fix Duration display and allow init from hi/lo values by ChristopherRabotin in https://github.com/nyx-space/hifitime/pull/105


**Full Changelog**: https://github.com/nyx-space/hifitime/compare/2.3.1...2.3.2

Enhancement
+ `Errors` now implements `std:err::Error` allowing it to be used as an actual error.

New features
+ Can now build a `Duration` by calling `.seconds()`, `.nanoseconds()`, etc. on several primitive types (unsigned and signed `int`s and `f32` and `f64`) (96).
Enhancements
+ Migrated the underlying computation from a generic lossless fraction to `TwoFloat`, a tuple of two 64bit floats to represent time. This led to an 85% reduction in computation time. (93)
+ Fix odd behavior of nanoseconds in string conversion (90)
+ Implement `FromStr` for `TimeSystem` for a cleaner API (95)
[Pull request here](https://github.com/nyx-space/hifitime/pull/99)