Word-wrap README files and rename them .md

This way, Github and other tools will know they're markdown and display them
accordingly.

It's also much easier to read when it's word-wrapped to 80 chars.

The lines including code or strings to be copied and pasted haven't been
word-wrapped.
Improved formatting of README files
Fix formatting of main README
Merge pull request #115 from sfu-natlang/documentation-update

Word-wrap README files and rename them .md