Support custom domains

[Glavin001]

Such as http://blog.glavin.org/ which goes to https://github.com/Glavin001/Glavin001.github.io

[Glavin001]

May not be possible. So far I can only find a response header Server:GitHub.com that indicates anything involving GitHub.

[Frozenfire92]

I thought of this initially and wasn't able to come up with a good way of determining if it was a github page or not. Initially I thought of scraping the website for any links to a github profile and then checking if that profile has a username.github.io repository that has a CNAME file that matches the url you are currently on. Obviously this adds a lot of overhead and this extension was designed to be quite lightweight. That solution also isn't guarenteed and can produce incorrect results.

Somewhat related to #11

Also this would require opening up permissions to all websites which isn't desirable either #10

If you come up with a way I would be interested to hear about it!