Improving equation solvers

by Harsh Gupta for SymPy

The project aims at improving the current equation solver in sympy by: 1. Cleaning up the input API for current solvers 2. Providing a consistent output format by returning sets. 3. Refactoring refactoring solvers to be more robust and reliable so that we can answer questions like, "have we found all the solutions?". 4. Implementing radical denesting and singularity finder.