Pytzer

* <u>Testing **MarChemSpec05** against **FastPitz** at 278.15 K - perfect agreement to 6 significant figures</u>;
* Added `theta_Ca_H_MarChemSpec` to combine RGO82 and WM13 equations;
* Added new module **pytzer.tables** to store long lists of coefficients found in tables;
* Added basic **tables** page to documentation, and new ions to the name conventions lists;
* Updated `bC_` functions for `Ca-SO4`, `Ca-HSO4` and `K-HSO4`:
* Used data from new **pytzer.tables** module;
* Relabelled from `P91` to `WM13`, to better reflect their provenance;
* Added `Aosm_MarChemSpec`, which adds a small offset to `Aosm_CRP94` to make it consistent with AW90 and FastPitz;
* Created new **MarChemSpec** **CoefficientDictionary**, with temperature-varying `Aosm_MarChemSpec`;
* Added equations and usage examples to documentation for **pytzer.model**;
* Wrote **pytzer.blackbox** function and quick-start documentation, for easy end-user testing.

* Testing activity coefficients against Prof D.R. Turner's and Prof S.L. Clegg's implementations (GIVAKT and FastPitz respectively):
* Assembled new **CoefficientDictionary** WM13_MarChemSpec25 for testing;
* Corrected `alph1` for **bC_Ca_OH_HMW84** to 2;
* Fixed temperature units for **theta_H_Na_CMR93** and **theta_H_K_CMR93**;
* Deleted duplicate MP98 functions in **coeffs**;
* Added functions with temporary values for 298.15 K for *λ*(tris, tris), *ζ*(tris, Na, Cl) and *μ*(tris, tris, tris) to **MarChemSpec25** **CoefficientDictionary**;
* <u>**pytzer** activity and osmotic coefficients agree perfectly (to 6 significant figures) with FastPitz at 298.15 K with the **MarChemSpec25** **CoefficientDictionary**</u>;
* Continued adding coefficient functions to **cfdicts.MIAMI**:
* All from PP82 (`Na-CO3` and `Na-HCO3` interactions);
* Added equations for neutral-neutral interactions (lambda coefficient) to **model.Gex_nRT** and also to **cfdicts.add_zeros** method;
* Changed to evaluating all neutral interactions (including with ions) even at zero ionic strength;
* Updated nomenclature for consistency with P91: `eta` (*η*) is now `zeta` (*ζ*).

* Verified both **jfuncs.P75_eq47** and **jfuncs.Harvie**, and their differentials, against Prof D.R. Turner's and Prof S.L. Clegg's implementations;
* Began assembling MIAMI **CoefficientDictionary** following MP98;
* Added constant <i>A_ϕ</i> function for 25 °C following P91 to **coeffs.Aosm_25** for MarChemSpec project testing.

* Added temperature to the file produced by **print_coeffs**;
* Improved documentation:
* Added neutrals, and made other updates, for **pytzer.coeffs**;
* Updated for **pytzer.cfdicts**;
* Added **pytzer.meta** page;
* Updated installation instructions;
* Documented new `Izero=False` input to **model.Gex_nRT**;
* Fixed zero ionic strength error for **model.Gex_nRT**;
* Removed `Jp` outputs from all **jfuncs**, and set up correct differentiation for `Harvie`;
* Corrected functions in **CoefficientDictionary** `WM13` following intercomparison with Prof S.L. Clegg's Fortran implementation:
* `bC_Mg_SO4_PP86ii`: eliminated *difference of two large numbers* error, by substitution;
* `bC_Na_HSO4_HPR93`: fixed incorrect charge for HSO₄⁻;
* `bC_Na_OH_PP87i`: fixed typos in coefficients;
* Switched **MarChemSpec** **CoefficientDictionary** to *not* use **GT17simopt** for `Na-Cl` interaction (stick with M88 instead);
* Fixed function for `H-Na-HSO4` interaction in **WM13** **CoefficientDictionary**;
* Added external package requirements (i.e. **numpy** and **autograd**) to the **setup.py**;
* Fixed **CoefficientDictionary.get_contents** to include neutral species;
* Added input `Izero=False` to **model.Gex_nRT** and its derivatives, to allow calculations for solutions with zero ionic strength.

* Fixed fatal indexing error in **model.Gex_nRT**;
* Added **CoefficientDictionary** `WM13` for the Waters and Millero (2013) model;
* Added **CoefficientDictionary** `MarChemSpec` for MarChemSpec project testing;
* Added *some* coefficient values from Gallego-Urrea and Turner (2017);
* Added equations for neutral solute interactions to **model.Gex_nRT**, along with supporting functions in **pytzer.cfdicts**;
* Added **CoefficientDictionary** methods:
* **print_coeffs**, to evaluate all model coefficients at a given temperature, and print them to file;
* **get_contents**, to generate lists of all ions and all references within the dictionary;
* Updated documentation on coefficient dictionaries to reflect these changes;
* Added **meta** module as single-source-of-truth for package version;
* Updated documentation with basic information on neutral solutes.

The first beta release, including full documentation on [pytzer.readthedocs.io](https://pytzer.readthedocs.io).