Vitess is now Hadoopable

Add GetMRSplits to VtGate client
Added VitessInputFormat, VitessInputSplit, VitessRecordReader
Writables for KeyspaceId and Row
Integration tests for MapReduce

Other minor stuff:
VT_LongLong maps to UnsignedLong instead of BigInteger
Get rid of byte array in KeyspaceId only keep id