GSoC peer review

Below are some reviews and I let you check them out.

Some commits concern the README by fixing typos and using some [markdown syntax](https://guides.github.com/features/mastering-markdown/).
Some others fix some of the PEP8 conventions (not all of them of course, read the [PEP8](http://legacy.python.org/dev/peps/pep-0008/) for that).
Some others use python standard features like `dict.pop(key)` instead of `dict[key] & del dict[key]`.