Use tuple modules instead of parameterized modules

Erlang/OTP R16, coming soon, will do away with parameterized modules
(see Issue 4 under http://www.erlang.org/news/35 for details). Change
QC to use tuple modules instead, since they will continue to be
supported in R16 and beyond. These changes are backward compatible, so
current applications should require only recompilation to continue
working.

Thanks to mochiweb and @vinoski for the inspiration for these changes.