**Summary:**
Fixes an issue with calculating currents with TPXO9-atlas models in netCDF4 format (thanks mirkorupani!). Changes how nodal arguments for constituents are calculated. Program now uses linear algebra with a table of Doodson coefficients (Cartwright numbers), which should hopefully be more transparent and extendable. This also allows the easy calculation of Doodson or Cartwright numbers for constituents (thanks q1165600785!).
**Itemized Changes:**
* `fix`: revert TPXO9-atlas currents changes to separate dicts for 258 (259)
* `test`: fix `u` and `v` for TPXO9-atlas netCDF (259)
* `fix`: escape sequences in docstrings to raw (259)
* `fix`: updated ssl context to fix deprecation error (259)
* `docs`: update docstrings for ssl context (259)
* `refactor`: use doodson arguments tables to calculate values (270)
* `refactor`: rename `phase_angles` to `doodson_arguments` (270)
* `refactor`: coordinate reference system class `crs.py` (270)
* `refactor`: pass through `VBox` and `HBox` in `tools.py` (270)
* `docs`: add link to TMD3 in `Resources.rst` (270)
* `feat`: made keyword argument for selecting M1 coefficients (270)
* `feat`: add initial solver for harmonic constants (270)
* `chore`: include whitespace after commas (270)
* `feat`: add function to create arguments coefficients table (270)
* `test`: add check that arguments match prior version (270)
* `docs`: started creating a glossary (270)
* `docs`: add citation to Simon et al. (1994) (270)
* `feat`: create arguments coefficients table for minor constituents (270)
* `feat`: add function to calculate Doodson numbers for 263 (270)
* `refactor`: use mean lunar time as independent variable (270)
* `refactor`: moved minor arguments calculation into new function (270)
* `refactor`: implicit import of arguments (270)
* `test`: add check for constants solve (270)
* `feat`: add functions to convert to and from Doodson numbers (270)
* `feat`: add option to output Cartwright numbers (270)
* `feat`: add properties for Doodson and Cartwright numbers to `constituents` class (270)
* `feat`: try to get the constituents of FES files (270)
**Full Changelog**: https://github.com/tsutterley/pyTMD/compare/2.0.9...2.1.0