pep8 fixes for processor tests
Remove utils.Accessor
Change processors to not need utils.Accessor, change tests accordingly
Change graphite backend and its tests to use the new way of accessing processors
Change graphite backend test's processor imports to be on a single line
Remove odd __call__ that somehow got left behind when utils.Accessor was removed
Use functools.partial to wrap up the parameter differences between AggregatingSummarizer and LastDatapointSummarizer
Merge branch 'feature/issue-76-get-rid-of-utils-accessor' into develop