Add required skills to projects

[jdm]

Looking at the homepage, I don't have a good sense for if a project requires skills (ie. programming languages) that I have. We should find some way to surface that information.

[wsmwk]

@jdm Are you referring to the fact that if you pick a project, that you can't filter further on skills? Likewise, if you filter on skills, then you get all (often unrelated) projects thrown at you?

If so, that's a pretty big deficency.