Redshift watcher and auditor

*Created a redshift watcher and auditor*
* The watcher simply calls to gather cluster descriptions
* The auditor simply looks for clusters outside of a VPC
* The UI is updated to have a redshift entry in the reports dropdown

*Refactored to add watcher concept and makes adding watcher and auditors easier*
* For each new watcher/auditor pair, the codebase required edits in a lot of spots:
  1. Add the new watcher and auditor. This seems very reasonable.
  2. Add ```find``` and ```audit``` entries in ```manage.py```. Most entires here are cut/paste of the previous and not very DRY. This should be refactored away.
  3. Add ```find``` and ```audit``` and ```run``` entries in ```security_monkey/__init__.py```. Most entires here are cut/paste of the previous and not very DRY. This should be refactored away.
  4. Add an entry in ```security_monkey/reporter.py```
* Simplified this by creating the concept of a ```watcher```
  - A watcher describes a watcher and associated auditor.
  - Adding a new watcher and auditor to ```security_monkey.monitors._MONITORS``` replaces the need for edits 2, 3, and 4.
 * As a side-effect, this fixes a bug where only some auditors actually had been configured with a reporter.
 * This changes the way ```manage.py``` is called.
  - Use ```python manage.py find_changes -m rds``` rather than ```python manage.py find_changes_rds``` 

*Refactored to simplify ```security_monkey/__init__.py```
 * These was a lot going on in dunerbar init and it started making refactor/adding code hard.
 * Tore out stuff around running and scheduling into ```security_monkey/scheduler.py```
 * ```find_XXX``` and ```audit_XXX`` were simplified to use monitors

*Minor Changes*
* Update .gitignore to hide a few dart related dirs not under source control.
* A bit of a refactor of security_monkey/__init__.py to DRY things.