Fix error_limit = 0, and make it the default

Setting the error_limit to 0 would previously cause rexi_server to crash
on the next error because of an unhandled exception in a queue:drop/1.
This fixes that exception and makes a limit of 0 the default. Operators
can still raise the limit to capture errors in the future if we end up
finding that useful.

BugzID: 30821
Merge pull request #26 from cloudant/30821-set-error-limit

Fix error_limit = 0, and make it the default

BugzID: 30821