removing customer.io sessionid
fix helpscout tests
Merge remote-tracking branch 'origin/fix/help-scout-tests'
customer.io: enforcing `userId`

Customer.io requires a `userId` field or else it will create a bunch
of duplicate users.
preact: relaxing `email` constraint, fixes #19

Preact doesn't require `email` fields as long as `uid` is sent as well.
0.1.20

  e6f3e4d  removing customer.io sessionid
  f3d58c1  fix helpscout tests
  5e74eb0  customer.io: enforcing `userId`
  3345d79  preact: relaxing `email` constraint, fixes #19