add option page

[jackhftang]

This is not a complete solution to fix #15 . However this should give a rough idea of how to create option page for users to configure in chrome extension.

Be aware that the month-bar is shortened (obviously). I tried to fix it, but I found that it would be better to rewrite part of app.coffee and restructure of app.jade. And I really do not familiar with the dev stack coffee + jade + d3.. and I do not want to rewrite a lot without original authors' permission. I can contribute more if you switch to stack javascript + html/react.js and I have in-depth experience with chrome extension.

BTW, I really ❤ this app.

[hychen]

Hi Jack

Thanks for your contributions, @kcliu will merge we may not consider to change dev stack and rewrite/restructure since we just have a designer joined development recently and will have a new UI design.

We may start to rewrite this app when new UI mockup done.

[jackhftang]

Nice, looking forward to the new UI =]