Removed the interface hierarchy from the Core.Events classes

.. because they are value objects and there is no need to mock them. Having these interfaces only creates extra complexity.

* Also added a base implementation for the NestingIncrease method
Add performance tests to compare various releases.
Merge remote-tracking branch 'origin/master'

Conflicts:
	YamlDotNet.RepresentationModel.Test/YamlDotNet.RepresentationModel.Test.csproj
	YamlDotNet.sln
Merge pull request #74 from rogernorling/simplify-core-events

Removed the interface hierarchy from the Core.Events classes