Tests passing
Docs: Fix typos.
Merge pull request #2114 from tochev/docs_fixes

Docs: Fix typos.
Task.signature_from_request must propagate reply_to for RPC backend.  Closes #2113
Merge branch 'master' of github.com:celery/celery
Merge branch 'master' of https://github.com/celery/celery into autoretry
Tests passed