H^2 in separate branch
incorporate feedback from pull request
Implement rewrite as Piecewise for Abs, sign and Heaviside (issue 3478)
Cleanup _eval_rewrite_as_Heaviside() method for Abs
regular derivative in latex, fix latex derivative bug
partial versus ordinary derivative in mathml
pretty-print partial derivative symbol
more sophisticated logic for deciding whether to use a partial derivative
incorporate github pull request feedback
incorporate suggestions from github pull request
check that no exceptions are thrown in the case of differentiation with respect to an integer
better use of booleans in assert
fix unhandled case
fix for python 2.5 compatibility
Implement is_rational method for trig (and inverse) functions (issue 3215)

    http://planetmath.org/encyclopedia/TheoryOfRationalAndIrrationalNumbers.html
    and http://en.wikipedia.org/wiki/Transcendental_function says that
    there is only trivial exceptional set for exp (and log) function.
    Then, same is valid for trigonometric functions.

    For example, lets sin(x) = y is algebraic number.  Then,
    from y = (exp(I*x) - exp(-I*x))/(2*I) (quadratic equation for exp(I*x))
    it follows exp(I*x) is an algebraic number.  But the
    exceptional set for exp() is just {0}, then x should be 0 and,
    thus, the exeptional set for sin(x) is {0}.
Implement Q.algebraic assumptions for exp/log and trig functions

    see 7c99ac8b6be9aecb and 1c1f7e38dbca9869e9b
correct path to ask_update.py in docstring
Add facts: Q.rational => Q.algebraic and Q.algebraic => Q.complex (issue 2019)
AskAlgebraicHandler.Number shouldn't return False, it's wrong!

    Instead implement Float method and return True for one (just as for
    rationals).
Implement Infinity and NegativeInfinity methods for AskAlgebraicHandler