And some tests

Tiny updates, nothing too serious

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

Heading towards pure VLE derivatives

The build matrix is already crazy

Closes https://github.com/usnistgov/teqp/issues/30

version 0.14.1

And get the parameters from the class

Closes #27