Updates to CompressedObjectStrategy to support more compression types

* Compression types are not yet dynamically configurable.
* Added a benchmarking system for topN to test the compression
* Updated pom.xml to include junit benchmarking
* added an Uncompressed option
Code reformat in CompressedObjectStrategy
Merge remote-tracking branch 'origin/master' into druid-0.7.x-compressionstrategy
CompressedObjectStrategy improvements

* Added more unit tests
* Now properly uses safe / fast decompressor for LZ4
* Now chooses fastest lz4 instance instead of only looking at Java implmentations
* Encapsulate ResourceHolder in try-with-resources to make sure they close correctly
Merge remote-tracking branch 'origin/master' into druid-0.7.x-compressionstrategy
Modified CompressedObjectStrategy to use 0xFF for Uncompressed
Fix CompressedObjectStrategy LZFCompressor to ignore error on close of ResourceHolder
Update CompressedObjectStrategy to try-with-resources but print log error if error while closing
Removed lz4Fast from CompressedObjectStrategy for compression since it is not currently used
Changed branching logic for LZFCompressor to return null only on error, and avoid checking in most circumstances
Removed empty function from CompressionStrategyTest
Merge pull request #850 from metamx/druid-0.7.x-compressionstrategy

Compression strategy changes