[Testing] Create TextGrid to RTTM converter function

[chrisbrickhouse]

A lot of data is stored as TextGrids and researchers who want to use this to evaluate performance on their data sets need a way to convert their TextGrids to RTTM. Create a function that takes a text grid and outputs an RTTM. See #12 and #17

• The RTTM Format is described in this README
• The Praat TextGrid format is described in this manual page
• TextGrids can be loaded using the textgrid python package, see kylebgorman/textgrid
• A pull request should include a script and a conversion of TestAudio_SnoopDogg_85SouthMedia.TextGrid to RTTM format.