Add tests that utilize water

[davidlmobley]

Since water is now properly supported (i.e. TIP3P, SPC), some of the tests should utilize water to test this handling.

[davidlmobley]

Partially resolved by #64 in that tests now include water (and water which is not at the end) but I should still update the tests to check that water is handled properly, i.e.:

• it occurs in the topology file where it is expected to occur, and
• it is TIP3P/SPC if that was asked for