Merge pull request #476 from ovatsus/master

Remove apiary provider (closes #468)
use mono 3.2.7 and fsharp 3.1.1.1 on travis
Merge pull request #478 from enricosada/travis_fsharp31

use mono 3.2.7 and fsharp 3.1.1.1 on travis
Disable URIpurify on mono to see if that's the problem
Prefetch the roots of Freebase provider so if there's an HTTP error it's reported by the compiler, to help debug #478