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.
Raise RuntimeError when gist is unavailable
Convert to integer before comparing. data.code is String
Fix for bottom margin in nested lists.
Add EditorConfig file for Ruby files
Add EditorConfig file for classic theme
Added robots.txt, with sitemap link
Added stringex and changed to use #to_url for create directory. To don't receive error in url to accented characters.
optimized order of styles and scripts in header
Disabled Rsync delete by default. Closes #787
Upgrade ruby version
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 "/".
Fixing English error pet-peeve.
Merge pull request #831 from parkr/english

Fixing English error pet-peeve.
Rakefile option for any additional rsync arguments

Added variable `rsync_args`
gist tag plugin now works with the latest changes GitHub gists and does not fail if you do not specify a filename.
Merge pull request #824 from liangsun/patch-1

To support url without domain name like /path/file
Merge pull request #844 from jsvensson/rsyncargs

Rakefile option for any additional rsync arguments
Titles in code plugins can have slashes in them. Closes #892
Removed unnecessary regex in code block plugin