[Backend] Generating CSVs of Frequency Distributions

[jebking]

Frequency Distribution Chart (currently on front page)

1a. User enters a word, presses submit button
1b. Sanity check on input (frontend and backend)
2. Backend generates a new csv file in /data
3. Backend sends (some JSON for a callback?) a message saying it's ok to try to load the new data now

[jebking]

@rob3rtroessler let me know what you think

[rob3rtroessler]

1-2 sounds good to me! Now we have to think about the visualizations & the data structures in detail. I will open a new issue and formulate a precise task.