v2.0.0

• The AtlasStream class has been updated to use the new WebSocket interface
• AtlasStream objects can now be iterated as an alternative to using callbacks
• There used to be both start_stream() and subscribe() methods which did the same thing,
  except that start_stream() had extra validation. This extra validation has been
  added to subscribe(), and start_stream() is now an alias to it.
• bind_channel() was renamed to bind(), although it is maintained as an alias, and
  there is a corresponding unbind() to remove a callback
• Deprecated event aliases were dropped, you have to use full event names like
  "atlas_result" and "atlas_metadata" when binding