HADOOP-8316: Update Dr.Elephant version number to 0.6.4-SNAPSHOT
HADOOP-8316: Update Dr.Elephant version number to 0.6.4-SNAPSHOT

qubole/dr-elephant,snithish/dr-elephant,shankar37/dr-elephant,bretlowery/dr-elephant-mapr,nntnag17/dr-elephant-1,qubole/dr-elephant,nntnag17/dr-elephant-1,nntnag17/dr-elephant-1,snithish/dr-elephant,shankar37/dr-elephant,snithish/dr-elephant,bretlowery/dr-elephant-mapr,qubole/dr-elephant,snithish/dr-elephant,bretlowery/dr-elephant-mapr,shankar37/dr-elephant,nntnag17/dr-elephant-1,shankar37/dr-elephant,qubole/dr-elephant,bretlowery/dr-elephant-mapr