Improved interface of options.html page

[nirajkaushal]

I updated options.html to give it interactive look.
Before(options.html)

After(options.html)

[gaborluk]

The use of standalone options pages has been deprecated since Chrome 40.

The new way of displaying options is in a modal over the Extensions page, preferably with "chrome_style": true specified in manifest.json so that some Chrome-specific CSS rules get injected into the modal to let it blend right in.

I might throw something together later for this.

Edit: And I did, but since I was clumsy enough to submit another pull request from my master branch earlier, I will wait until it's reviewed and hopefully merged, and then start fresh with a fork and submit the update for the options page from that.