Implement AJAX based submission and edits

[sourabhtk37]

The following needs to be done to improve UX:

• (Optional) Implement Ajax for code submission and then update page using push state
• Once submission is done, watch changes in the textarea (codemirror editor) and update DB through AJAX call.

Another thing to simplify the process even more is to have the app directly give us a pad instead of homepage i.e, page will open with domain.com/app/<hash_value> instead of domain.com. This would enable us to implement AJAX easily and would be great for UX.