Corrected repr/str in thermopack_state

[morteham]

No description provided.

[vegardjervell]

is there a reason for accessing the _T and _x attributes directly instead of using the T and molefrac property's? Even though these are "internal" methods, I think consistently using the property's is good practice, in case we ever change them to do some error handling, value validation etc.

[morteham]

No - I have changed the code to use temperature and molefrac instead of the internal state variables

[vegardjervell]

Nice :)