Refactored format.py unit tests.

Also refactored/decomposed various functions in format.py to be easier to test. The unit tests shouldn't be such a pain to maintain now.

This fixes #97.
Merge branch 'master' into issue_97

Conflicts:
	my_microbes/format.py
	tests/test_format.py
Merge pull request #101 from jrrideout/issue_97

Refactored format.py unit tests.