Pitch statistics

This pull request adds a tool able to compute some statistics about the pitch extracted form the corpus.

The praat script has been modified in order to save some auxiliary files (the raw f0 data), and to extract the pitch with the very accurate flag set on: 
noprogress To Pitch (ac)... 0 minPitch 15 yes 0.03 0.45 0.01 0.35 0.14 maxPitch

The script pitch_statistics requires Octave.