Improve RC script (#1033)
Improve RC script (#1033)

* Remove unnecessary portions (comments about
  release:prepare/release:perform)
* Add SHA512 sums to thread
* Use more variables to generalize the script (helps keep in sync with
  Accumulo's release script)
fluo-io/fluo,keith-turner/fluo,ctubbsii/fluo,fluo-io/fluo,ctubbsii/fluo,keith-turner/fluo