Update to work with GitHub new design

Fix repo size and github pages button to work with new design #12

fix github pages url when repo name is username.github.io

Close #10, thanks @quericy for reporting this.

Add options to show unread or participating notifications

fix #9

Fixes multiple buttons when forward and back

fixed #7

v0.8.1

Add 'GH Page' button in project home page if it has enabled github pages.
Add 'download' button in file detail page.

[Feaure]Show Repo Size

Thanks to @yakiang 's advise.

The repo size is ambiguity, it's not the downloadable 'zip' file size, neither the cloned repo size.
Anyway, it's a dimension of the Repo , still meaningful, and these is no way to get the accurate size currently.

Refers:
http://stackoverflow.com/a/8679592/1219343

http://developer.github.com/v3/repos/#get

Create options page and make everything configurable

Merry Christmas and this is quite a sweet release.

In the options page, you can choose whether to enable click-to-download file feature, or disable annoying notifications feature. or set the frequency of notifications checking.

v0.3.1

bump to version 0.3.1

refine code structure