2.28.0

Reuse more of the NuGet v3 API for protocol selection
Using new NuGet v3 protocol to retrieve unlisted packages - #1254
Created installer demo - #1251
Adding monoandroid41 framework moniker - #1245
BUGFIX: Specifying prereleases did not work with pessimistic version constraint - #1252
BUGFIX: Unlisted property get properly filled from NuGet v3 API - #1242
BUGFIX: Bootstrapper compares version per SemVer - #1236
PERFORMANCE: Avoid requests to teamcity that lead to server error
USABILITY: If parsing of lock file fails Paket reports the lock file filename - #1247