change **airbrake to **kwargs
add airbrake_error_from_logrecord

includes style/docstring updates
change name to _notifier
util fn for checking a sys.exc_info() tuple
raise Exception if missing api_key or project_id
always use_ssl and auto_notify, remove the kwargs

removes the use_ssl and auto_nofity attributes/options

The airbrake endpoint will now always use the ssl scheme with https,
and the log() method will always call notify() when it has finished
building the error payload to post
use _context instead of _env_context
updates logic in Airbrake.log() and notifier.Error

addresses remaining comments from PR#8
add mock to test requirements
fix tests