Switch to github.io, as http://rogerdudler.github.io/git-guide/

[sturem]

http://rogerdudler.github.com/git-guide/ no longer works as Github Pages subdomains under github.com are deprecated. Github now recommend setting up using github.io, as http://rogerdudler.github.io/git-guide/

(unfortunately last update was June 2017 and last batch or merged pull requests was Jan 2017, so this might not happen here)

[msscsh]

Duplicate of issue #193
Solved in PR #185

This issue needs to be closed @sturem