use jaconv instead of jcconv for japanese chars

jaconv is available for more Python-versions and seems to be more
professional. Apart from that I added jaconv to the test-requirements
but not the requirements. (If the katakana-stuff really works we can
later add it as a real dependency)

tox.ini

@@ -3,6 +3,7 @@ envlist = py27, py34, py35, docs
 
 [testenv]
 deps = nose
+       jaconv
        coverage
        scripttest
        mock