Added new methods in ApiUrls:
- RepositoryCommitsSince (gets commits from a repo since a specified date)
- RepositoryCommitsUntil (gets commits from a repo until a specified date)
- RepositoryCommitsBetween (gets commits between 2 specified dates)
- RepositoryCommitsBranch (gets commits from a specified branch)
- RepositoryCommitsBranchDate (gets commits from a specified branch between 2 dates)
- added User method to retreive User information
Merge branch 'Repository_Commits_filtered_by_date' of github.com:Sebyd/octokit.net into Repository_Commits_filtered_by_date

Conflicts:
	Octokit/Helpers/ApiUrls.cs