Increase version to 2.0.0 and update release notes

[akamsteeg]

(Blocked by #26)

FINAL TASK BEFORE RELEASE

Checklist:

1. Create a release/v1.0.0 release branch from master
2. Ensure all feature & fix branches are merged back to release/v2.0.0
3. Update version (assembly + package) to 2.0.0 in release/v2.0.0
4. Update the release notes with all finished tasks
5. Update readme.md with changed target frameworks
6. Merge release/v2.0.0 back to master
7. Create a new v2.0.0 release on Github with the release notes
8. Tag release v2.0.0 from master
9. Push release/v1.0.0 to origin
10. Push master to origin
11. Push tag v2.0.0 to origin
12. Delete branch release/v2.0.0 locally and remote
13. Release through VSTS