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
small fixes
adding tests for features to come
more vector and constraint tests
switched matrix tests to arrays
changed tests to match dictionary interface
small error
Early matrix/vector support

a reimplemetation of the numpy matrix class, with:
 - slightly different printing
 - convenient element-wise functions
 - overloaded <= for constraint generation
Added matrix functions to __init__ and utils
swapping out lambdas
Switched from numpy matrices to numpy arrays
Made imports absolute ('gpkit.array', not 'array')
require monomials to have positive c
pep8
Updated readme, notebook, and gitignore
Updated readme, notebook to new GP class interface
Geometric Program obj with constants substitution
typo
readme tweaks
Added MOSEK support: twice as fast as CVXopt