Update text on front page

This is just a reminder to update the content on the homepage to reflect 0.2.

I was also wondering whether it would make sense to reword *The Astropy project is a common effort to develop a single core package for Astronomy that brings together almost 100 developers from around the world.* as '100 developers' is a little ambiguous - we have 130-140 people on the dev list, but only ~30 developers have actually contributed code. Maybe we should just say *The Astropy project is a community effort to develop a single core package for Astronomy.* and then merge into the start of the 2nd paragraph.