add dicttoolz

Move merge_dict to dicttoolz
add keymap, valmap
PEP-8 fixes
Merge branch 'pep8-fixes' into dicttoolz-additions

Conflicts:
	toolz/itertoolz/tests/test_core.py
Merge pull request #3 from eigenhombre/dicttoolz-pep8

A few PEP-8 tweaks
Merge pull request #4 from mrocklin/dicttoolz

Dicttoolz