bump version to 0.4.5
Merge branch 'master' of github.com:mrocklin/multipledispatch
Resolve returns None if no match is found

NotImplementedError is raised only when trying to call, not resolve
Merge branch 'master' of github.com:mrocklin/multipledispatch
Merge branch 'master' into resolve-none

Conflicts:
	multipledispatch/dispatcher.py
Merge pull request #36 from mrocklin/resolve-none

Resolve returns None if no match is found