PE-5845 NC - Creating a group with diacritical marks (áéíóúäëïöüñçâê) 

Diacritics not displaying properly

There was unnecessary (slurp) call which converts stream resource to Java string.
And somewhere in this conversion diacritics is lost. This patch makes it so that
request body is not touched at all. Instead of asking for empty body, we are asking
for desired HTTP request method and comparing it with list of officially supported
HTTP methods in http://hc.apache.org/httpcomponents-client-ga/httpclient/apidocs/org/apache/http/client/methods/HttpEntityEnclosingRequestBase.html
@cprice404 We used contrib.io in our initial attempts to work around the problem. However, it's better to support entity buffering in clj-http-client (in a different way, using apache BufferedHttpEntity - there's another PR on it), so I believe we don't need contrib.io (nor java.io) here any more (see my note below).