Uptodate copyright.
Updated nuget build script where build number can be passed in or, if ran in appveyor, is detected. The nuget package version is read from the $psake.Version value from psake.psm1.
Fixes error if VS 14.0 installed and VS 12.0 is not

Existing code throws exception if  Visual Studio 14.0 is installed and
Visual Studio 12.0 is not. Changed to verify key exists before
retrieving it.
Actally let's make this version 4.4.0
Merge pull request #124 from kinyubi/master

Fixes error if VS 14.0 installed and VS 12.0 is not