Fixing samples to be shipped for CTP3

This also includes some of the samples project.json feed discussed like remove version attribute, changing case of Kestrel to 'kestrel'
Fixing the nuget.config feed to point to the new feed for master.
Fixing readme with a pinned build of KRE.
Merge pull request #122 from aspnet/fixmasterfeed

Fixing samples to be shipped for CTP3
Adding instruction to get KRE from master feed.