Refactor NuGetV2.followODataLink to take a function to get the url contents so that a stub can be injected for testing.
Add regression test for https://github.com/fsprojects/Paket/pull/393

Cosmetic changes within NuGetV2.fs
Merge pull request #397 from jvrdev/master

Regression test for https://github.com/fsprojects/Paket/pull/393