Refactor

[camilleanne]

To do:

Transition the guts of pulse into a browserified node application.
v1 (operates with just the green channel):

• transition from flask to node app
• modularize front end (move to a new repo)
  • make data filter configurable
• tests

v2 (uses ICA on all channels):

• implement or find a js implementation of ICA
• use ndarray
• more tests