Removed debug logging.
Javascript code cleanup.

Added Occurrences class.
Fixed CSV quoting issue.

The ngram*.tsv and posts.tsv files were in the same format as the
infodump files: tab-delimited, no quoting.  The GAE bulk uploader was
being confused by " characters, and there is no way to tell it to use a
CSV dialect without quoting.  The solution is to write out quoted files.

This fixes #5 and #6.