Fixed blog_url not returning & rake setup_github_pages failing

When executing `rake setup_github_pages`, an error tells that `url` don't exist. The reference to that variable has been changed to a call to `blog_url`.

The function `blog_url` was not returning anything, failing to properly write the `_config.yml` file. It now does return what should have.
Fixed blog_url when user contains uppercase letters
Made blog_url becalled just once...

...and stored in the `url` variable.
Fixed issue with RubyPants and the Octopress hooks filter
updated compass
enable wildcard of rm_rf
Merge pull request #1658 from kamatari/fix-rake-clean

enable wildcard of rm_rf
Merge pull request #1331 from Darkhogg/patch-1

Fixed setup_github_pages failing and not properly writing url to _config.yml
Add link to add site to the wiki

So that more people will do it and it'll take less time. As long as we trust people, that's good.
leave some hints about OP3.0 (not mentioned on imathis/octopress and not at octopress.org )
Fix 1656 - & needs specific quoting under Windows
Merge pull request #1684 from tangledhelix/feature-windows-ampersand

Fix 1656 - & needs specific quoting under Windows. Closes #1656.
Rakefile: use source_dir when setting url via CNAME
Google broke old site-search method, this fixes it
Fix the way of loading the local copy of jQuery

Deleted the dot at the beginning of the path in the script that called the local copy of jQuery.
Merge pull request #1699 from VincentTam/jquery-ref

Fix the way of loading the local copy of jQuery
Merge pull request #1687 from blbradley/rakefile-cname-sourcedir

Rakefile: use source_dir when setting url via CNAME
Merge pull request #1682 from muescha/patch-1

leave some hints about OP3.0
Merge pull request #1678 from Blaisorblade/patch-1

Add link to add site to the wiki
Merge pull request #1657 from enriquesaid/master

updated compass