Extract category_link filter from category_generator.rb plugin

Allows category_link to be used as a filter to display a link to
any category.
Added robots.txt, with sitemap link
To support url without domain name like /path/file

You need to know if you would like to support this, each word in the title can not start with "/".
Rakefile option for any additional rsync arguments

Added variable `rsync_args`
Removing public/ from .gitignore to enable deployment to heroku
First version
gist tag plugin now works with the latest changes GitHub gists and does not fail if you do not specify a filename.
Titles in code plugins can have slashes in them. Closes #892
Removed unnecessary regex in code block plugin
updated gems
Rake task new_post now accepts titles through stdin
This should help resolve issues for zsh users and make it easier to enter titles which freak out Rake's argument processing
removed accidentally added file
Escape github repo descriptions, as they may contain HTML.
updated ender.js to latest
Whitespace
Improved error message for category_generator plugin. Addresses #116
Fixed blockquote plugin (author alone would not show up without title)
Striped whitespace from titles in blockquote plugin
Video tag plugin now supports mp4,ogv,webm formats, closes #931
setup_github_pages: allow for clones missing .git extension