Adding simple unit tests.
Merge pull request #11 from EducationalTestingService/feature/add_unit_tests

Unit Tests
Merge branch 'develop' into feature/parse_tagged_sent
Added `parse_tagged_file()` and `dep_parse_tagged_file()` function to parse pre-tagged files.
Added pre-tagged data file.
Expose `parse_tagged_sentence()` and `parse_tagged_file()` on the python side.
Added new tests for parsing tagged sentence and file.
Added methods to dependency parse tagged sentence and file.
Added new tests for dependency parsing of tagged sentences and file.