Constrain index names to ASCII so we do not create latin-1/UTF-8 conflicts down the road
Index names are converted to binary much earlier in the process, so we must convert them back to a list before running dropwhile
Reject characters below whitespace per @coderoshi
Merge pull request #381 from basho/jrd-ascii-indexes

Constrain index names to ASCII to duck latin-1/UTF-8 conflicts

Reviewed-by: coderoshi