test for issue 2073
XFAIL in gruntz for 2073
Merge branch 'master' into 2073-tests

Conflicts:
	sympy/series/tests/test_gruntz.py
Merge pull request #2326 from skirpichev/2073-tests

Tests for issue 2073 (limit pass, gruntz fails with a wrong answer)
Added functions code
Added tests
Added doctests, rectified default params and tests