doc_len replaced with dt.row_sum
remove doc_len method and file loading
remove doc_len reference
remove doc_len file writing
ensure model navbar elements hidden on load
dfrtopics mentions
extra TODO note on brushes
first working version of topic-word viz

tried but failed to do a version using a regular old table. This does
the table using svg instead. The tilted words are not SO easy to read
but it does allow me to fill the page with information.

FIXME: the transitions in both x and y produce a lot of clutter and need
smoothing out.
better transitions

pretty kludgy with the delays and durations, but somewhat more
acceptable as a user experience.
word_view svg width
a little help text for the word_view