Implement rewrite as Piecewise for Abs, sign and Heaviside (issue 3478)
Cleanup _eval_rewrite_as_Heaviside() method for Abs
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
in latex: don't use operatorname for single letter functions; properly render functions without arguments
fix quantum printing tests