[2to3port] Remove unused files

Reuses: 9ad5314a90bcaf244434cd90e3fa0d9f2cab5cba
[2to3port] Update installation instructions and add a "contributing" section

Reuses: 309388d30b957043a8b450af324d4920c6950823
[2to3port] Step through the first few doc pages and do style adjustments

Reuses: 93ff1ea89dca62f02152e24f074229b10071fb30
[2to3port] Add a simple index for the API docs

Reuses: 54bfe369cb97424ff4ea06d12ec8408422ceca42
[2to3port] Add contents parameter to "open_file" command

Reuses: 53ed507748fe12cf0bb3f4595646bc2fb6f77cf8
Merge branch 'ff-edits-11' into sublime-text-3
Merge branch 'ff-edits-12' into sublime-text-3
Merge branch 'ff-edits-13' into sublime-text-3