Merge pull request #1 from efontana/master

Syncing with upstream
Elastic output improvements

FIX  Existing implementation only took one element from the queue per loop rather than clearing the queue.
ADD  Clients can submit a custom index that is being leveraged if specified. If not specified, the output reverts to a statically configured index name.
Merge pull request #9 from hardcodet/custom_index

Custom index