Use a createElement method to create elements

Make code cleaner
Restructure methods in inject.js
Update TODO

Author: sidvishnoi

TODO

@@ -1,2 +1,3 @@
 get api key via login
+improve keyword highlighting
 readme, presentation, video and stuff

contentscript.js

@@ -112,7 +112,7 @@ asyncParallel({
     injectScriptText(`
       console.log('<<< fbDevInterest >>>');
       fbDevInterest.parent.innerHTML = '';
-      fbDevInterest.getFeed();
+      fbDevInterest.init();
     `);
   });
 });