Added two tests - both fail because of mutton-detach issue.
Modifed c_src/Makefile to remove Mutton leveldb on clean.
Removed trailing whitespace from c_src/Makefile.
Found issue w/ the `hanging` on 2nd run related to this.
Added logging to stderr when error blocks entered.
Reworked strategy for registering Lua scripts w/ Mutton.
Added comment about redirecting stderr for external program.

Turns out that `rebar` appears to redirect stderr to stdout when you
are running eunit tests.  Much of my effort to have this logging sent
to a file was overall not helpful.  But I've learned something about
rebar and can hopefully troubleshoot issues in test faster next time.
Discovered `failure` test case that hangs emtn_prog.