Tests for 'filtering' feature( https://github.com/soulseekah/Gravity-For...

Fixed issues relating to earlier pull request ( https://github.com/soulseekah/Gravity-Forms-Digest-Bulk-Reports/pull/17 ).

This updated pull request addresses the following items:
- https://github.com/soulseekah/Gravity-Forms-Digest-Bulk-Reports/issues/12
- https://github.com/soulseekah/Gravity-Forms-Digest-Bulk-Reports/issues/13
- Increment version of gravity forms that is downloaded by tests/init-test-environment.sh

There a few comments in pull request 17.
These remain applicable in the current pull request (you may wish to view if you have concerns).

Cheers.