Update install instructions and quick start guide

A bunch of things were outdated in Chaco's quickstart guide. This updates the following:
- Replace EPD by Canopy for the easiest way to install chaco.
- Remove the links to old Chaco/ETS and to svn.enthought.com since they are not active anymore
- Recommends Qt and `pip` over WX and `easy_install`
- Added a section on Where to learn more?
- Added a section on How to report a bug or contribute a patch.

Feedback welcome.
Should this be updated to Enthought Canopy (formerly EPD) as well?