Update Rakefile to allow for ssh aliases

I usually set up my remote github URL as

github:username/repo

where 'github' is an .ssh/config alias that picks the right username and
key, like so:

````
Host github-r7
Hostname github.com
User git
PreferredAuthentications publickey
IdentityFile ~/.ssh/path_to_private_key
````

This kind of configuration is handy for people like me that have a
billion keys for a billion different sites.

The logic change is simply to invert the match and meaning of .nil? --
if the user picks https, then use the https protocol format to pick the
user. Otherwise, pick the username out from the ssh-style format.
Have a .ruby-gemset and .ruby-version

Without these, it gets easy to stomp on an existing default global
gemset when using a Ruby installation manager like rvm.
Merge pull request #14 from todb-r7/allow-for-ssh-aliases-for-rake-setup_github_pages

Update Rakefile to allow for ssh aliases