intercom: adding impressions for track and identify

Intercom logs impressions for users in order to increase their
session count. This adds that for track and identify calls.
intercom: removing ip and useragent from user update

In order to actually update the session count, the user's last
seen ip and useragent must not be the same as the incoming ip.
Now that we record an impression, we can remove those from
the update call
Merge branch 'master' of github.com:segmentio/integrations
release: 0.1.4

 fe82229 intercom: removing ip and useragent from user update
 07806a4 intercom: adding impressions for track and identify
removing testing data
intercom enabled fix
Removed default event value from being set to '1'

This behavior is different between the back-end tracking integration and the front-end: https://github.com/segmentio/analytics.js/blob/master/lib/integrations/google-analytics.js#L117

I personally prefer it not to default to anything, because it screws up our value tracking on events that don't have a dollar value, but either way the two libraries should remain consistent.
webhooks: increasing retries

Retrying for occasional webhook hiccups
Add support for USERcycle.
usercycle: adding extra docs and initial cleanup
Merge remote-tracking branch 'mattsjohnston/patch-1'
release: 0.1.5

  9eaad4f  webhooks: increasing retry count (calvinfo)
  7055390  usercycle: adding support for usercycle (lfittl)
  ded1f94  google-analytics: removing default value set to '1' (mattsjohnston)
librato: updating user-agent with segmentio version
release: 0.1.6

  6a0d6ef  librato: updating user-agent with segmentio version (calvinfo)
Add Mixpanel special property $username to identify.
webhooks: adding request timeout
release: 0.1.7

  2141dee  webhooks: adding request timeout
google-analytics: checking for value, removing default value

Edits events to remove values by default.
release: 0.1.8

  ba2b15f  google-analytics: checking for value, removing default value
Merge remote-tracking branch 'brianpmarks/master'