Fixing Test For Data not fitting in a block

    * Added additional check for data length before writing to block
    * Fixed the "exceedingBlockSizeTest"
Merge branch 'Fix_BrokenTest_For_DataSizeExceedingBlockSize'

Conflicts:
	src/main/java/de/jhoff/dmap/DMapBuilder.java
	src/test/java/de/jhoff/dmap/DMapBuilderTest.java
DMapBuilder Update : Adding Info in Global Trailer

    *   Updated DMapBuilder to store first key of a block along
        with the block offset info in the global trailer. This
        is to allow DMap to efficiently query for a key.

    *   Updated DMapBuilderTest to verify the latest changes
DMap update for restructured Map File

    * Refactored DMap class to reflect the change in map file structure.
    * CachingHashMap to limit block info stored.(Oldest entry removed)
    * FIXED: ByteArray compareTo : compare unsigned ints instead of
      signed bytes.
    * Added new ByteArray utility class.
    * Updated test classes.
Clean Up DMap_changes