add github repositories sidebar plugin

if you specify

github_user:

in you _config.yml and once you add asides/github.html to your sidebar
items, this plugin will fetch the specified users github repositories
and order them so the last pushed ones are shown first. Then it'll list
them in the side-bar, including a link and the repository description

The plugin will only list your own repositories, not forks, though this
might need to be configurable later
allow limiting the amount of repos to display

by setting github_repo_count to someething that's not 0, you can limit
the amount of repositories to render
provide an option to show or not show github profile link
make listing/not listing of forks configurable

some people have more or less taken over projects with their forks, so
it probably makes sense to still list them among the repositories
corrected fork skipping logic
Static Server based on Sinatra

Using Sinatra provides better handling of mime types and supports
304's/etc.

Also updated the Gemfile to exclude most gem outside of developemnt
(default).
using @extend for responsive blocks, added shadow-box mixin to utlities for configurable border shadow box styling, moved .left, .right, .center classes to .basic-alignment class for @extending as needed in layouts. Fixes #109
updated Gemfile.lock, fixes #59
updated date now shows up properly
Makes update_source and update_style much more windows friendly.
Removes system specific File IO from Rakefile, rather we make use of FileUtils.
Do not rely on system specifc syntax for preview or watch.
sleeps wait, cleaned up rake preview and rake watch a bit
removed unnecessary mkdir_p in update_style, fixed #67
Added warning if users try to add posts, pages, or generate their site
before installing an Octopress theme, fixes #116
Somehow I replaced Rakefile with oder version, oops
sitemap_generator dies if public dir doesn't exist yet

this tests for the presence of the public dir and creates
it if needed. This situation can arise in a new install.
removed octopress.org rsync deploy config from Rakefile. Oops
not using cd in copydot, breaks chained task when further cd's are called
Merge pull request #123 from rtgibbons/master

rsync deploy broken (fix included)