ReSharper 8 support.

ReSharper 8 support:
- VS2012 only
- NUnit/XUnit breaks runner
Clean build for ReSharper 8
ReSharper 8 nuspec file
Updated project info attributes
Removing support for R# 6 and 7.

Users of earlier R# versions should use the previous AgUnit releases.
Fix build: Update StatLight
ReSharper 8 support.
Visual Studio 2010 and 2013 support.
Bump version number.