To fix "enter" bug, replace button created by <a> tags with a form submit button that has same id. Form can now be submitted by hitting enter or by clicking button, with same functionality.

 - Changed app.js to listen for form submit
 - disable #visualize input
 - In index, create input type=submit, give it button class and id #visualize
Use time module to test individual code blocks on length of processing time. Remove other print statements.
Capture time using time.time(), print out the difference between t0 and t1 at key stages in flask process.
 - Time to get initial user
 - Time to get friend ids
 - Time to paginate friends
 - Time to get timeslines and score

Friend pagination takes a long time for "whales" with many friends.
Time to get timeslines and scores is uniformly long (15 seconds) for users with 50 friends and users with 1800 friends.
Removed time.time() calls, time-delta print statements, and out-of-date comments.
Remove time.time() testing markers.
Add header above progress bar, letting user know that friends are being analyzed for the user. When success callback is called, empty message.
Change screen_name to screenName in app.js. Add extra layer of validation to remove @ symbol if a user enters it.
WIP - adding error handling to try/except statements, although this needs to be put on pause until after MVP is complete.