parallel coordinates of topic distribution can be written to a json or a
.js file with "topics" variable
added folder with D3 visualization scripts. Currently holds an html for
rendering parallel coordinate plots with brushing.
rewrote make_parallel_coords.py to work with the D3 html script. **NEEDS
TESTING**
changed the name of D3 folder for simplicity. Also, the .js file with
variables for plotting is now saved directly in the appropriate D3
folder.