Add DvnFile object, add dvn_test for running tests, bug fixes, improvements

-add support for a custom service document uri (to make it easier to
connect to non-dvn sword servers for testing)
-add is_released() method on Dataverse
-add get_study_by_string_in_entry() to search for study by title, etc.
-add DvnFile object for listing and deleting files from studies
-rename some methods on Study object
-update Study.get_files() to use the DvnFile object
-add update_metadata() method to study
- add release() method on a study to release it
- add delete_file() method on study to delete a DvnFile from a study
- add delete_all_files() method on study
- fix bug with ZipFile < 2.7
- add get_citation() method on study
- add internal _refresh() method on study to update it when we make
server calls
-update get_elements() to handle blank namespaces
-update puppet to clone github and install swordv2
-add dvn_test.py which uses the python unittest framework to run tests
against dvn_client

Bonus:
update .gitignores