Snakebacon

Minor patch mostly fixing compile issues and documentation.

Bug fixes
* Documentation spelling errors.
* Fixed bad compiling C++ module (Issue 19).

A patch with minor refactoring and bug fixes.

Bug fixes
* All `*_kwargs` arguments are now `*_kws` (Issue 12).
* Fixed some Constant Calibration curve prior dates looking bloated (Issue 14).
* Fixed bug from default `t_a` and `t_b` values in `calibrate_dates()` (Issue 13).
* Fixed bad label in prior accumulation memory plots. The 'thick' had been 'K'. This has been corrected.
* Fix AttributeError in `AgeDepthModel.plot_prior_dates()` (Issue 9).

A quick patch to fix a show-stopping bug.

Bug fixes
* Fixes missing curves for bacon MCMC fitting (Issue 7).

Enhancements
* `DateRecord` class has been renamed `ChronRecord` to avoid confusion with `DatedProxyRecord` (Issue 3). The` read_chron()` is also now `read_chron()`.
* `AgeDepthModel` instances now can plot prior distributions. <https://github.com/brews/snakebacon/issues/19>`_
* Can now query `AgeDepthModel`s to get prior distribution for chronology dates, sediment rates, and sediment rate memory (Issue 5).
* Now can use `snakebacon.mcmcbackends.bacon.fetch_calibcurve()` and the `registercurve()` decorator to define and fetch calibration curves by name (Issue 6).
* `McmcSetup` and `McmcResults` now throw bacon its tasks through `mcmcbackends.Bacon`. This should make snakebacon more bacon-agnostic. Have a look at `McmcSetup`’s `mcmcbackend` arg.
* `suggest_accumulation_rate()` is no longer a method, but a humble function.

Bug fixes
* Fixed common `AssertionError` in `AgeDepthModel.agedepth` caused by float precision bug (Issue 4).
* Fixed problem with `ProxyRecords` and `DatedProxyRecords` not making copies of Pandas `DataFrame` attributes. (Issue 2).