Also test dipolar with JSON

The references seem to be getting broken. There must be an implicit copy somehow.

Added into the coeffs structure, nice interface

Need to decide on how to handle the model composition with the chain models

Refactoring of the SAFT contributions is going to be needed

And some tests

Can also specify them as JSON-formatted string, to make fitting a bit easier, for instance

Typo in Thorade for dp/drho|T, missing factor of 2

See #21

Closes https://github.com/usnistgov/teqp/issues/15

* Adding the 2-Center Lennard-Jones model developed by Mecke and the revised version of Lisal

* Added dipolar and quadrupolar contributions to 2CLJF model

Add conversion routines for ideal-gas Helmholtz terms from CoolProp format

Yet another forceeval

Add routine for TP flash for binary mixture, to solve for molar concentrations (and therefore mole fractions)

Found the first real bug in autodiff: https://github.com/autodiff/autodiff/issues/242

And add test

See https://github.com/usnistgov/teqp/issues/9

Should speed up compilation a smidge

A polish was needed after perturbation (duh!)