Fixed issue 3538. Subs working in .n()
Added test
evalf_trig handles complex arguments without raising exceptions
Merge branch 'master' of https://github.com/sympy/sympy into evalf-trig-iss3538
Merge pull request #1736 from prasoon2211/evalf-trig-iss3538

Passing a dictionary to .n() now works on cos and sin. Issue 3538