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`
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
removed accidentally added file
Escape github repo descriptions, as they may contain HTML.
Merge pull request #914 from rixth/master

Escape github repo descriptions, as they may contain HTML.
updated ender.js to latest
Whitespace
Merge pull request #936 from richo/cleanup/whitespace

Whitespace
Improved error message for category_generator plugin. Addresses #116