Issue #227: Allow charset encoding in content-type field
Issue #233: Move content subtype removal into RiakClient
Issue #227: Moved management of content-type back into RiakObject
Issue #227: Re-re-reimplmented charset breakout in the http transport layer
Issue #227: Clean up pep8 and pyflakes (and @seancribbs) warnings
Issue #227: Fix unit test and RFC-compliant quoting of charset
Issue #227: Commit correct file version
Merge pull request #233 from basho/bch-content-charset

Issue #227: Allow charset encoding in content-type field for HTTP