Issue #3581:Implement arg.rewrite(atan2)
mark some solve tests as slow
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
Fix issue #3738
Add test cases for issue #3738
Add other two test cases
Merge pull request #1928 from amitjamadagni/trig

Issue #3581:Implement arg.rewrite(atan2)
simplify -1 and I handling in Mul.flatten

The best of 3 runs of the core test suite gave, in seconds,

master: 43, 48, 57
now: 36, 36, 45

So this appears to be a little faster and leads to a more compact result.
watch for unevaluated I**e
remove errant print statement
Merge pull request #1991 from mrocklin/remove-print

remove errant print statement
Merge pull request #1989 from lidavidm/issue_3738

Fix issue 3738
Merge pull request #1987 from smichr/n1

-1 and I flatten better in Mul.flatten