@NonNull
    public static Single<Response> postRequest(final String uri, final Parameters params, final Parameters headers) {
        return request("POST", uri, params, headers, null);
    }
POST HTTP request

@param uri     the URI to request
@param params  the parameters to add to the POST request
@param headers the headers to add to the request
@return a single with the HTTP response, or an IOException
main/src/main/java/cgeo/geocaching/network/Network.java