Session recording updates

This releases bundles several updates and fixes for the session recording feature:

• New debugging method mixpanel.get_session_replay_url() returns a mixpanel.com link to view the current replay if there is an active recording taking place.
• The record_inline_images configuration option has been removed for now due to buggy behavior in the rrweb library.
• Recording payloads now include additional metadata: the current URL, library type, and library version.
• Sourcemaps are now generated for the recorder module.
• Added some additional error handling for when mixpanel.stop_session_recording() fails or rrweb silently fails to start recording.