Web api for dynamically adding checks

..and dockerfile that is a bit more efficient at rebuilding python changes

This is still a WIP but I would like to get a bit of feedback
OK I think I have it worked out, for example to keep last 3: 
```
                ln = self.db.llen('results:%s' % self.stream.id)
                if ln > 3:
                  self.db.ltrim('results:%s' % self.stream.id, ln - 3, ln)
```

Now we can set it to some reasonably high value - say 10000 - as long as it is bounded - is fine - only so many checks can be run anyway due to nupic memory usage ;) (or we can use some heuristic and option) - thoughts?