[scikit-image] Website updates

[Stefan van der Walt]

Hi, everyone

I worked with a student to clean up the website a bit.  Because it's
hard to review a website via diff, I made the plunge and uploaded the
new pages.

I'd be grateful for feedback, especially on:

http://scikit-image.org/
http://scikit-image.org/docs/dev/auto_examples/ (notice sidebar, notice
boxes)
http://scikit-image.org/docs/dev/

and

http://scikit-image.org/docs/dev/api/api.html

Thanks!
Stéfan