4.2.0 (2017-09-28)
[FIXED] Fixed an issue where pusher-js would not attempt to subscribe to
channels that were in the process of being subscribed to when the connection
failed.
[FIXED] Does not attempt to call handlesActivityChecks on an undefined
connection instance anymore. Fixes issues #82 and #233.
[NEW] More helpful error messages can now be logged, with URLs.
[CHANGED] Various improvements in README.md.
Many thanks to @hengwoon, @leesio, @juliangruber and Heng for their
contributions to this release!