Blog about cause support

We might want to fold the monkeypatch from the cause gem into the
Bugsnag gem itself as I suspect most people won't upgrade to 2.1
immediately.
Actually mention the ruby notifier
Draft 2
re-write v1
+missing image
Trim "debugging" section
Plug @avdi's post
Link release announcement too
Some quick style changes for conrads post
Link to original_exception docs for ActionView::Template::Error
Another link, minor copy tweaks
Consistent titlecase, crop screenshot