Add metrics collection to Sherpa

[jdmedlock]

Track Chingu usage and attributes of Sherpa

• number of times sherpa interacted with per week or month
  (this will allow us to see the effectiveness of sherpa and/or if we need to iterate to make the bot more accessible)

• number of times someone uses a foreign language with sherpa
  (this will let us know how much future resources should go towards projects related to functionality besides English)