Add a count function to rqworker.py.

`Count` returns the number of queued jobs to a Redis queue.
Also add a log message stating that work has begun.
Pin dependencies in setup.py and requirements.txt

Add missing pusher requirement.
Some package versions were update in the process.
Refactor of ec2.py, ccouchdb.py and cache.py.

ec2.py:
 - Add function `get_hostname`.
 - Fix bug terminated instances returned by all(). All instances were returned
   and not just those running.

cache.py:
 - Better host retrieval.
 - Remove the connection pool instantiation. Redis is already using a
   pool by default.
 - Fix incorrect env variable name: REDIS_URL -> REDIS_HOST.

ccouchdb.py:
 - Add a update_feed function. Returns a continuous feed of update to a given
   database.
 - Can be called as a script to sync a design document written as a YAML file
   to a given database.
 - Add EC2 service finding capability.

[#47442765]
Add twitter.py, sync setup.py with __init__.py.
Add decorators.py.
Merge pull request #10 from ooda/marketsense-improv

Modifications following marketsense.io refactoring.