Fix Issue 3727 (ufuncify + erf)
Staging the infra of a basic PDE Solver
Minor Change
added ``minimal_polynomial_sq`` and ``nthroot``

``minimal_polynomial_sq`` returns the minimal polynomial for the
``nth-root`` of a sum of surds.

``nthroot`` computes a real ``nth-root`` of a sum of surds.
Added util.py- helper functions
Made all changes except ode_order
modified ``minimal_polynomial`` to call ``minimal_polynomial_sq``;
solved issue 2895
Improved documentation and cleaned up test failures
code cleanup
Add Sphinx doc building to Travis
Updated sphinx docs
Use an older version of Sphinx, which is known to work

This is to work around https://code.google.com/p/sympy/issues/detail?id=3623.
Echo each command from test_travis.sh
Implemented TODO's
faster minimal_polynomial for sum of surds
minimal_polynomial_sq renamed _minimal_polynomial_sq
[integrals/meijerint] Fix a bug in _split_mul.

This fixes issue 3761.

_split_mul tries to write an integrand as c*x**a*f, where a and c are
independent of x. However, it did not actually test that a is independent
of x ...

Fix this, and add the test from the issue.
[integrals/meijerint] replace e.has(x) by x in e.free_symbols
Merge pull request #2015 from ness01/3761

Fix issue 3761.
Merge pull request #1953 from thisch/issue_3727

Fix Issue 3727 (ufuncify + erf)

http://code.google.com/p/sympy/issues/detail?id=3727
theano print Matrix and ImmutableMatrix