Change pygromacs.utils to Google style docstrings
Move pygromacs.gmxfiles module docstrings to Google format
Add module docstring
Clean up tests and make them use temporary directories

Additionally removes the workaround of MdpFile.save returning
a path to an eventual backed-up file since it was an ugly
workaround to implement testing

MdpFile.search now returns number of items found after a
unit test was implemented to control for it

Adds more tests for comments and set_options
Docstrings switched to Google style

The Napoleon extension for sphinx has been implemented
to accomodate the switch
Merge branch 'change_return_from_print' into working

Conflicts:
	pygromacs/gmxfiles.py
	pygromacs/utils.py