Merge pull request #1 from marekpetrik/python3_compatibility

Python3 compatibility
fixed mistake in comment
Merge branch 'develop' of https://github.com/ajwdewit/pcse into develop
docs add for PCSE design and code. Now skipping unittest for FROSTOL.
Cropped the figure to make it a bit smaller.
Merge branch 'develop' of https://github.com/ajwdewit/pcse into develop
Updated documentation: API docs compile, user guide was added.
Deleted some superfluous files under doc/
updating code docs to allow module index building.
Merge pull request #1 from ajwdewit/develop

Develop