[WIP] Redo website yet again

early stage.
Now with online build: http://amueller.github.io/scikit-learn/

![asdf](https://f.cloud.github.com/assets/449558/851757/6aa92000-f4a2-11e2-834d-05e2e0d244e7.png)


Todo:

- [x] Fix text on front-page
- [x] Fix links to sections on front page
- [x] Fix text on documentation page
- [x] Fix links on documentation page
- [ ] link to older versions of docs
- [x] remove old version warning on install
- [x] fix blue bar on front page
- [x] fix sponsor images
- [x] fix lowest part: community etc.
- [x] fix copyright notice
- [x] fix collabsible sidebare
- [x] fix collabsible toctree
- [x] fix prev / next buttons
- [x] layout on the first page
- [x] drop-down documentation link in menu
- [x] fix broken link on the first page (testimonials, donations "read more", changelog)