support playlist changing, shuffle, and repeat mode control

lib/spotify.js

@@ -99,6 +99,10 @@ function Spotify(config) {
     });
   };
 
+  this.playContext = (uri) => {
+    return spotifyApi.play({"context_uri": uri});
+  };
+
   this.skip = () => {
     return spotifyApi.skipToNext();
   };
@@ -117,6 +121,14 @@ function Spotify(config) {
     if (volume > 100) volume = 100;
     return spotifyApi.setVolume(volume);
   };
+
+  this.shuffle = (state) => {
+    return spotifyApi.setShuffle({"state": state});
+  };
+
+  this.repeat = (state) => {
+    return spotifyApi.setRepeat({"state": state});
+  };
 }
 
 module.exports = Spotify;