Refactored monos, added many features to posys

 - Created a template 'nomials' class for shared features
 - added 'eid' attribute to monomials (it's basically a hash of 'exp')
 - added algebraic simplification to both monomials and posynomials
 - added posynomial-posynomial multiplication
I'm seeing at least three functions in that window, but I'm guessing you mean 'simplify'? If so it's just adding together any monomials that add to another monomial, which along the way also removes duplicates (and thus makes sets happier).

There's a simple test for it in the 'tests' branch.