Initial Frontleaf integration

Adds ‘Frontleaf’ as an integration.

Supports identify, group, and track methods.
Remove external dependency

Pulls code into mapper for smaller merge risk
Merge remote-tracking branch 'upstream/master'
Don't use forEach for better backwards compat.
customerio: when the id is an email send it as .email too
Merge pull request #93 from segmentio/fix/customerio-email

customerio: when the id is an email send it as .email too
Update mapper.js
webhooks: adding transform

To fit with the new spec
Merge branch 'add/webhooks-transform'
Release 1.1.21
adding automatic aliasing for kissmetrics, fixes #95
only alias if you have a sessionId and a userId
Merge pull request #97 from segmentio/fix/kissmetrics-alias

adding automatic aliasing for kissmetrics, fixes #95
kissmetrics: auto-alias cleanup
Release 1.1.22
kissmetrics: fix merge error
Release 1.1.23
frontleaf: updating
Merge branch 'pr-79'
Release 1.1.24