Fix existing tests for changes made as part of the igtools update

[jranalli]

This updates the tests for the ideal gas classes to match the basics of the new functionality.

• Remove the invargs error check (there's not an error with too many invargs anymore)
• Update the test entropy values for air to match the new entropy calculation including smix
• Change the h&s and e&s tests to test values rather than testing for them to error

It's important that you merge these tests in, because there are several major functionality-breaking bugs that were introduced in the edits to the ig classes. I have identified many of them and can start to propose fixes, but we've got to update the tests first.

TODO:

• Write tests for the new igtools module comparable to current state of test_ig at least
• Incorporate testing of Gibbs & Helmholz and speed of sound for all substances done
• Look for other tests that have been invalidated double checked, looks ok

[jranalli]

Two of the TODO's are sorted out. There are definitely some failed tests in here that indicate bugs. I do have code to address some of them.

[jranalli]

Ok I have a draft of the entire test suite based on your changes completed.

Of 12,541 tests, 2,350 currently fail.

The majority are easy fixes, like a changed variable name that got missed elsewhere, etc, so once we update the tests, we can start addressing those and look at what expansion of the tests is warranted.