v5.1.0

[NEW] Include typescript declarations

[CHANGED] Make stats opt in rather than opt out - Previously we sent some
metrics about connection strategies to stats.pusher.com by default, it could be
disabled by passing the disableStats option. This functionality is now off by
default and can be enabled by passing the enableStats option

[FIXED] An issue where local tests would hang for 300s if a browser wasn't
available