Moved _version2int to utilities module

Also removed _version2tuple
Updated cython files with parameters.pxi file
Added maximally mixed state
made reordering function names more explicit
updated sparse tests with new names
updated steady state solvers and testing functions

- added weighted_bipartite_matching to reordering

- added new eigen solver

-much updated power solver

-combined iterative methods into single function

- dropped support for bicg solver as the new scipy.sparse.linalg docs
suggest that this method works for Hermitian, positive definite
problems only.