add os x build script and upgrade travis to mono 3.4.0
upgrade nuget.exe
delete repositories.config - this is generated during build
upgrade to newest FAKE - this adds @files@ in the nuspec file for explicit naming of files.
Adjust nuspec creation.
use different download url for mono.
Add support for negative test cases
Merge pull request #12 from DanielFabian/feature/FixCIAlsoForUnixySystems

Feature/fix ci also for unixy systems