Batch Rollup Writes
add configuration values for rollup batching. instrument rollup write time
add tests to RollupExecutionContextTest relating to batching
update all tests to use Write Contexts
handle failures during rollup appropriately
Merge pull request #1 from fourk/batch_rollup_writes2

Batch rollup writes part 2
Merge remote-tracking branch 'racker/master' into batch_rollup_writes

Conflicts:
	blueflood-core/src/integration-test/java/com/rackspacecloud/blueflood/service/MetricsIntegrationTest.java
	blueflood-core/src/main/java/com/rackspacecloud/blueflood/io/AstyanaxWriter.java
	blueflood-core/src/main/java/com/rackspacecloud/blueflood/service/LocatorFetchRunnable.java
	blueflood-core/src/main/java/com/rackspacecloud/blueflood/service/RollupRunnable.java
	blueflood-core/src/main/java/com/rackspacecloud/blueflood/service/SingleRollupReadContext.java
	blueflood-http/src/integration-test/java/com/rackspacecloud/blueflood/outputs/handlers/HttpRollupHandlerIntegrationTest.java
merge aftermath
push failed slots to the end of the ordering
Merge pull request #155 from fourk/batch_rollup_writes

Batch Rollup Writes