Use username arg for follow and unfollow requests.

Author: CodyGramlich

lib/User.js

@@ -150,7 +150,7 @@ class User extends Requestable {
     * @return {Promise} - the promise for the http request
     */
    follow(username, cb) {
-      return this._request('PUT', `/user/following/${this.__user}`, null, cb);
+      return this._request('PUT', `/user/following/${username}`, null, cb);
    }
 
    /**
@@ -161,7 +161,7 @@ class User extends Requestable {
     * @return {Promise} - the promise for the http request
     */
    unfollow(username, cb) {
-      return this._request('DELETE', `/user/following/${this.__user}`, null, cb);
+      return this._request('DELETE', `/user/following/${username}`, null, cb);
    }
 
    /**