Revamped

It's been Pavelized, everything combed through and rewritten. The biggest user-facing change is the support of (and preference for) keyword arguments, but methods have also been corrected, expanded, reorganized, extended to handle variable step sizes where possible, given better tests, integrated with improved optimization code, documented thoroughly, and been put through a head-to-head performance analysis. All while removing about 2000 lines of code to make it more readable, manageable, and understandable. Enjoy.