Add Subscriber and IronmqSubscriber

- Add support for receiving pipeline messages in a Rails app
- Add IronMQ push queue subscriber endpoint via Sinatra
- Add script for setting up endpoints as subscribers
Fix minor test failures

- Scope of 'topic' changed in refactor
- Rename redis queue to avoid conflict with harry's app running
Add switches to disable pipeline and add config to README
Fix sinatra dependency
Add NewRelic tracking for subscriber
Read options as string not symbols for ironmq_subscribe_endpoint
Publish the event type with the model

Event type is an enumeration {CREATED/UPDATED/DELETED}
Add default subscriber handler if the target class doesn't define one

Apply basic CRUD operations:

- Create the object for the CREATED event_type
- Delete the object for the DELETED event_type
- Update the object for the UPDATED event_type
Add notes about register's DSL
Add before_script in travis to setup test db

Fix dummy app for travis
Convert double back to datetime in subscriber
Move default handler to specific handler class
Add basic logger handler
Add api key to the EncryptedMessage. Verify the api key on subscriber

- Emitter has to define PIPELINE_API_KEY
- Subscriber has to define PIPELINE_API_KEYS

Subscriber accepts a comma separated list of api keys through the env
variable PIPELINE_API_KEYS, that allows an easy rotation of keys
Fix New Relic instrumentation, using nested transaction doesn't work
Implement version fallback in receiver class

If class doesn't implement the received version, try to fallback on the
closest, lower, defined receiver method.

Added a thin wrapper around version to stop doing s.split('_')
everywhere we need to handle major/minor
Add method caching for emitter and subscriber

Cache result after first lookup into #methods and #instance_methods to
avoid this "expensive" lookup.

Store the value in a hash as version => method_name
Decrease iteration count to create AES key to 10000
Merge pull request #1 from harrystech/subscriber

Add Subscriber and IronmqSubscriber