Doc patch for 3.0: replace @gen.coroutine with @gen.engine.

The oauth 1.0 redirect methods are asynchronous even though they don't
take a callback, so we don't want the end of the coroutine to trigger
a call to self.finish.
Copy .gitignore update from master to branch3.0
Update twitter base urls to use api 1.1 and HTTPS.

This is in preparation for the shutdown of version 1 of the API on
June 11.

Closes #809.
Version bump and release notes for 3.0.2.
Merge branch 'branch3.0'

Conflicts:
	docs/releases.rst
	setup.py
	tornado/__init__.py
	tornado/auth.py
gen.coroutine works with auth now so we can use it in the docs.