0.7.7

• Fix a bug that would not capture request bodies if they were empty JSON
  arrays, objects or strings.
• New GNU backtrace integration parses stacktraces from exception messages and
  appends them to existing stacktrace.
• Capture Tornado formdata.
• Support Python 3.6 in Sanic and AIOHTTP integration.
• Clear breadcrumbs before starting a new request.
• Fix a bug in the Celery integration that would drop pending events during
  worker shutdown (particularly an issue when running with max_tasks_per_child = 1)
• Fix a bug with repring locals whose __repr__ simultaneously changes the
  WSGI environment or other data that we're also trying to serialize at the
  same time.