fix twisted recipe
Update toolchain.rst
Update prerequisites.rst

More clarification, after 
https://groups.google.com/forum/#!topic/python-android/jaK9rA9ZWa8
Update usage.rst

Added explanations
Added protobuf recipe
Add a storm/psycopg2 recipe

This should allow using python-storm (https://storm.canonical.com/) and
psycopg2 for connecting to a postgresql database.
add recipe for cprotobuf
Merge pull request #295 from yihuang/master

add recipe for cprotobuf
Merge pull request #292 from romaia/storm

Add a storm/psycopg2 recipe
Merge pull request #287 from minou/master

Added protobuf recipe
Merge pull request #285 from jdruiter/patch-3

Update usage.rst
Merge pull request #284 from jdruiter/patch-2

Update prerequisites.rst
Merge pull request #283 from jdruiter/patch-1

Update toolchain.rst
Merge pull request #282 from kived/twisted-fixes

fix twisted recipe