Fix some typos and text in HTTP Utilities

Signed-off-by: Timothée Boucher <timothee@gmail.com>
Remove circular link to documentation root

On http://werkzeug.pocoo.org/docs/,
http://werkzeug.pocoo.org/documentation/ links back to
http://werkzeug.pocoo.org/docs/

Maybe it linked to previous versions' docs before?

Signed-off-by: Timothée Boucher <timothee@gmail.com>
Add link to community page in Installation intro

Where it says to contact devs if you want to use Python 3
Fix few typos and little things on Transition page



Signed-off-by: Timothée Boucher <timothee@gmail.com>
Fix typos, punctuation and missing word in Tutorial

Signed-off-by: Timothée Boucher <timothee@gmail.com>
Fix typo in "API Levels"

Signed-off-by: Timothée Boucher <timothee@gmail.com>
Fix some typos and punctuation in Quickstart

Signed-off-by: Timothée Boucher <timothee@gmail.com>
Fix typo in Transition

Signed-off-by: Timothée Boucher <timothee@gmail.com>
Merge pull request #259 from Timothee/docs_fixes

Docs fixes in "Getting Started" section