Add TreeDefinition.Add(string, TreeEntry)
Add rewrite test that injects existing TreeEntry
Fix building with Mono on OS X
Fix broken tests on OS X
Extension methods for NoteCollection using user from config

Similar to Repository.Commit, NoteCollectionExtensions.Add/Remove take the committer and author signature from the global git config user.name / user.email. This allows modifying notes without specifying the commiter explicitly
Tests create global config stub if required

Instead of relying on the global configuration and skipping the test if
Git is not installed, the following tests create a configuration file
containing user.name and user.email using
BaseFixture.CreateConfigurationWithDummyUser(Signature):

* CommitFixture.CanCommitWithSignatureFromConfig()
* ConfigurationFixture.CanEnumerateGlobalConfig()

Fixes #561
Enforce Network.ListReferences() test coverage

This puts under the light that DirectReferences may point to GitObjects unknown from the local repository.
Improve Network.ListReferences() documentation
Enumerate refspecs

The Remote.RefSpecs property allows to enumerate over all refspecs defined for a specific remote.
Update libgit2 binaries to 98eaf39

https://github.com/libgit2/libgit2/compare/e87d9d3...98eaf39
CommitLog can be sealed because it has interface
Add test for interface coverage

Closes #546
Fix undisposed stream in test
Refactor git_branch_iterator
Introduce Proxy.git_iterator
Add Configuration.Find(regexp)
Remove unnecessary global config check
Introduce repo.Committish(es)
Introduce Repository.Blame
Publicize Configuration.BuildSignature()