minor optimizations to astyanaxwriter
- updated Configuration to include ElasticSearch.
Add DiscoveryWriter and DiscoveryIO interface

The DiscoveryWriter class is used to record metric names to a backend
implementing the `DiscoveryIO` interface as new metrics come in. This
will later allow for querying for metrics using wildcards, as well as
getting a list of all metrics.
Initial commit of elasticsearch discovery backend
Make blueflood-elasticsearch a maven module
Move embedded ES server into tests so tests can find it
Do not use enum singletons
add missing deps
remove crufty comments
Comparing classes with != can fail in unpredictable ways
Only add metric units to annotation info if not null
No need to hold onto futures in async process chain
misc simplification
Add unit test for DiscoveryWriter
implement fixes suggested in PR
Merge branch 'master' into es-discovery

Conflicts:
	blueflood-core/src/main/java/com/rackspacecloud/blueflood/service/Configuration.java
	pom.xml
fix DiscoveryWriterTest unit test
Use new configuration pattern

Also support more than 1 seed ES server.
fix tests
Add method to load all configured discovery modules