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 "/".
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
Merge pull request #408 from dtchepak/category_link_filter

Extract category_link filter from category_generator.rb plugin
updated gems
Merge pull request #537 from joseprio/master

robots.txt generation
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