Make requests to Riak Search support non-ASCII text

- Encode text as UTF-8 when making query strings
- Encode assembled XML as UTF-8
- Responses are in JSON, which natively handles Unicode already
Merge branch 'master' of https://github.com/LuminosoInsight/riak-python-client
add httplib.BadStatusLine as a retryable error
Merge branch 'pr/210'

Conflicts:
	riak/transports/http/__init__.py