STORM-69: Storm UI Visualizations for Topologies

Adds a directed-graph topology visualization to the topology page using storm's metrics and a javascript library called 'Arbor.js' released under the BSD license.

Features:
- Colors to represent spouts and bolts: spouts are blue, bolts are colored between green and red depending on their capacity consumption

- Width of lines between components represents the flow of tuples going between the components relative to the other visible streams.

- Stream selector: Select the streams you want to see.

- Tuple count, name, and latency labels on nodes and edges


![storm-visualizations](https://cloud.githubusercontent.com/assets/1819836/3121975/bf60b42a-e761-11e3-8c44-bf605362b5a1.png)