Update py-sympy to 1.2

Highlights

  There are many changes in 1.2 (see below). Some of the highlights are
    * Python 3.3 is no longer supported. If you require Python 3.3
      support, use SymPy 1.1.1. See our [518]policy on dropping support
      for major Python versions.
    * Experimental LaTeX parsing with sympy.parsing.latex.parse_latex()
      has been added, based on the latex2sympy project. This requires
      antlr-python-runtime to be installed. [519]#13706
    * The vector module has been improved to support orthogonal
      curvilinear coordinate systems ([520]Szymon Mieszczak's GSoC
      project)
    * New module sympy.integrals.intpoly for integrating uni/bivariate
      polynomials over 2-polytopes. ([521]Arif Ahmed's GSoC project)
    * Improvements to the code generation module. ([522]Bj?rn Dahlgren's
      GSoC project)
    * Improvements to the group theory module. See below for more
      information. ([523]Valeriia Gladkova's GSoC project)
    * New module sympy.discrete for operating on discrete sequences.
      polynomials over 2-polytopes. ([521]Arif Ahmed's GSoC project)
    * Improvements to the code generation module. ([522]Bj?rn Dahlgren's
      GSoC project)
    * Improvements to the group theory module. See below for more
      information. ([523]Valeriia Gladkova's GSoC project)
    * New module sympy.discrete for operating on discrete sequences.
      ([524]Sidhant Nagpal's GSoC project)

Complete release notes at:
https://github.com/sympy/sympy/wiki/release-notes-for-1.2

(prlw1)