merge_with raises err on no inputs
only toolz.curried.merge_with fails on no dicts
remove toolz.merge_with from do_curry set
Merge branch 'master' into merge-with-no-inputs

Conflicts:
	toolz/tests/test_curried.py
Merge pull request #73 from mrocklin/merge-with-no-inputs

merge_with raises err on no inputs