Implement handler extension to TTL-expire events
Fix rubocup errors and warnings

Mostly return values and replacing single-quote strings with
double-quote strings. One instance where an inner loop was moved into a
method, but the constant value it needed didn't ride along.
misc style and function fixes

Mostly symbol->string changes but also fixes a number of logical errors
resulting from e.g. method extraction
Merge pull request #577 from StephenWeber/ttl-handler-extension

Implement handler extension to TTL-expire events