Move the "Testimonials" out of "Learn"

[bbatsov]

I don't think they belong there, so perhaps they should be under "Community"?

[IanWitham]

Agreed

[dsyme]

I think put them in a top level navbar item of their own.

The testimonials are probably the most important unique content in the site. They are the "social proof" for F#. They are emphasised in the front content, which is great, but I think a top level navbar item is warranted as well.