ignore SassTests on build server (#294)
update to libsassnet 3.0
- add constructor to SassPreprocessor allowing user to control precision
- base relative path adaptation on web paths instead of disk locations
- this **should** help with rewrite issues when combined assets are read
  from / written to network shares and such (#297)
- need to add tests
remove obsolete network path code/tests from RelativePathAdapter
relative path adaptation refinement
- (hopefully) better represent what is actually going on and minimize
  weirdness
remove Nuget.CommandLine reference, not sure where that came from