v3.0.0

This release adds support for automatic and custom breadcrumb tracking.
Breadcrumbs replace the private implementation of "last event" tracking.
It also removes support for the deprecated userId setting, which has been
replaced by the user object.

Enhancements

• Add support for sending "breadcrumbs" - notable events leading up to an error
  Christian Schlensker
  #149
• Send device time in error payload
  #165