[WIP] Rewriting the Univariate Solver

This PR aims to rewrite a cleaner and robust univariate equation solver.
- [ ] Univariate
    - [x] polynomial
    - [x] rational
    - [ ] trigonometric
    - [ ] functions with exp and log
- [ ] Multivariate
On Sat, Aug 09, 2014 at 10:22:37AM -0700, Matthew Rocklin wrote:
>    I thought that assume= was also intended to work with new assumptions.

Yes.  As well, as "with assuming".