more nomials refactoring

 - new equalities (now eid- and c- instead of string-based)
 - cleaner and faster simplify code
 - use of defaultdicts for eid (means that any non-named variables returns
   a 0 instead of an error)
 - removed non-dict interface to making a monomial
Merge branch 'master' of https://github.com/appliedopt/gpkit into om

Conflicts:
	gpkit/nomials.py
small fixes
Merge pull request #14 from bqpd/om

Nomials refactoring