HADOOP-8134: Release Dr. Elephant v0.6.3
HADOOP-8134: Release Dr. Elephant v0.6.3

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