HBase Storage

Here's the start of an HBase storage module.  It's still in pretty early form but I wanted to get this up so that reviews could start early.


## Tables
* zipkin.traces
* zipkin.idxService
* zipkin.idzServerSpanName
* zipkin.idxServiceAnnontation
* zipkin.ids

## Internals

I created a non-blocking futures based version of HBase's HTable.  This HBaseTable uses a thread pool to execute the calls to HBase.

Currently it's using HBase 0.95 (dev version).  This was chosen in the hope that this will be ready before the next release of HBase.  I can change this to 0.94 (stable version) if work progresses quickly. 

## Still ToDo

* Specifications are being weird with before vs beforeSpec
* Need to create all of the indexes.
* Clean up