Switch to using the Github API

[Potherca]

I've been looking at the current (new) implementation, and it seems to me that with one specific change, several issues could be started to be resolved.

The change I am talking about is switching from using the raw link of a given gist to using the Github API. If this switch was made, the all of the following issues could then be implemented:

• Gist.io for documents in a full repository? Gist.io for documents in a full repository? #70
• Support multi-file gists which have one markdown file Support multi-file gists which have one markdown file #75
• Put title in <title> put title in <title> #43
• Add author and date at the header Add author and date at the header #20
• Support private gists Support private gists #17
• Show author avatar if the gist isn't anonymous Show author avatar if the gist isn't anonymous #2

Or, in other words, all of the issues above would require using the Github API.

I've made a first working draft with an example implementation. Please note that it is not pretty (I still need to clean it all up), it was mostly to get an idea of what you think.

(Feel free to ignore my example implementation and re-implement it any way you please).

You can see my code here: #112

[datenreisender]

Looking at the issues above, many of them are already solved by the new implementation anyhow, right? Of course it still would be fine to fix more of them!

[Potherca]

Updated issue description with current status of issues.