Add Bundler support

[btuduri]

Hello,

After reading the issue #109, I do these little updates which manage jekyll’s dependencies when you had bunder utility. (cf http://gembundler.com/ )

Sincerly,

Benoît

[btuduri]

Thanks you @heathermiller for your answer. :)
To go back with bundler, it’s a ease to upgrade your gem because you can said to the updater, in my jekyll workspace (here), i need a particular version etc. It’s really awesome and non intrusive stuff.
Have a nice day.

[btuduri]

I close the pull request because it is open since a long time...