Add comments to improve clarity of code
Turn hard-coded arguments to cmd line arguments

Previously, arguments in the script like verbosity and training data files were
hardcoded into the script. We now make the user supply these arguments through
the command line, for flexibility.
Test word2vec model qualitatively

Script prints out words that are similar to a number of test words. e.g.
'demonstrated' should be similar to 'indicated', etc.