Fixed get_changesets filter criteria problem

- prepare filter criteria with AND operator for get_changesets
- fixed typo in test function name from last commit
- changed date ranges for get_changesets tests with date criteria
(test data is only between 2010-01-01 - 2010-01-03)
- extra test with all criteria (start_date, end_date, branch_name)
Merge pull request #114 from Tefnet/tefnet

Fixed get_changesets filter criteria problem