Implement Comparable inteface on Locator

Implemented the Comparable inteface on Locator to fix a
ClassCastException error. Here's the full error:

    java.lang.ClassCastException: com.rackspacecloud.blueflood.types.Locator cannot be cast to java.lang.Comparable

This occurred when using the contains method on some Set class to see if
the Locator was already present in the container.

Fixes batched reads in my dev environment. :)
Merge pull request #302 from dlobue/locator_implement_comparable_batch_fix

Implement Comparable inteface on Locator
Add batched meta writes method to AstyanaxWriter
Add batched meta reads method to AstyanaxReader
Add batched interfaces for meta fetch and push in MetadatIO
Add ability to use the batched methods for meta fetch and push for metadata cache
Add instrumentation around scanMetrics and checkMeta
Log the entire exception in RollupType cacher on cache exceptions
Place holder methods in MetadataCacheIntegrationTest
Add AstyanaxMetadataIO integration test
Add test cases for batched mode for meta reads and writes
Merge pull request #308 from lakshmi-kannan/bf_batched_meta_reads_writes_merge

RFR: Batched meta reads and writes