Switching to POST request and encoding "keys" in POST body when "keys" p...

Switching to POST request and encoding "keys" in POST body when "keys" parameter is present.

Using a keys query array as query param in a GET request does not seem to work very well (At least for me working with a BigCouch instance the keys are ignored completely). The CouchDb documentation suggests to use a POST request with the requested keys encoded in the post body (this works in my setup).