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
mark some solve tests as slow
Merge pull request #1931 from hacman/hacman

bugfix, consistency fix
Merge pull request #1956 from skirpichev/3478-rewrite-to-Piecewise

Implement rewrite as Piecewise for Abs, sign and Heaviside (issue 3478)
Add Ben Fishbein to the .mailmap file
Merge pull request #1979 from smichr/slow

mark some solve tests as slow
Merge branch 'master' of github.com:sympy/sympy