add guild emoji methods (#742)

* add guild emoji methods

* run docs

* crawl pointed out some things about the docs, so i fixed

* actually run the docs on the changes 🤦

src/structures/Guild.js

@@ -552,6 +552,43 @@ class Guild {
     return create.then(role => role.edit(data));
   }
 
+  /**
+   * Creates a new custom emoji in the guild.
+   * @param {FileResolveable} attachment The image for the emoji.
+   * @param {string} name The name for the emoji.
+   * @returns {Promise<Emoji>} The created emoji.
+   * @example
+   * // create a new emoji from a url
+   * guild.createEmoji('https://i.imgur.com/w3duR07.png', 'rip')
+   *  .then(emoji => console.log(`Created new emoji with name ${emoji.name}!`))
+   *  .catch(console.log);
+   * @example
+   * // create a new emoji from a file on your computer
+   * guild.createEmoji('./memes/banana.png', 'banana')
+   *  .then(emoji => console.log(`Created new emoji with name ${emoji.name}!`))
+   *  .catch(console.log);
+   */
+  createEmoji(attachment, name) {
+    return new Promise((resolve, reject) => {
+      this.client.resolver.resolveFile(attachment).then(file => {
+        let base64 = new Buffer(file, 'binary').toString('base64');
+        let dataURI = `data:;base64,${base64}`;
+        this.client.rest.methods.createEmoji(this, dataURI, name)
+        .then(resolve).catch(reject);
+      }).catch(reject);
+    });
+  }
+
+  /**
+   * Delete an emoji.
+   * @param {Emoji|string} emoji The emoji to delete.
+   * @returns {Promise}
+   */
+  deleteEmoji(emoji) {
+    if (emoji instanceof Emoji) emoji = emoji.id;
+    return this.client.rest.methods.deleteEmoji(this, emoji);
+  }
+
   /**
    * Causes the Client to leave the guild.
    * @returns {Promise<Guild>}