Log Message:
math/py-sympy: Update to 1.4

Highlights:

* Logic expressions with relations can now be simplifed in a better
  way which has impact on e.g. simplification of piecewise
  expressions.
* The MathML Presentation printer has seen a major improvement with
  support configuration and about a hundred new functions.
* Union and Intersection have been improved to, among other
  improvements, support Python sets.
* The test procedure has been changed to include code coverage and
  code quality checks leading to a number of issues being identified
  and removed.
* Unicode support, especially for Python 2.7, has been improved.
* subs and Subs have been improved in a number of ways.
* SymPy objects now renders as LaTeX automatically in Jupyter
  notebooks. init_printing is still required to LaTeX render non-SymPy
  objects such as lists of expressions or Python ints.