Move tasks into explicit namespace block

This isn't necessary, but it lets me fold away the guides tasks.
Add tasks to update blog.rubygems.org upon release

Now blog.rubygems.org will be kept up to date with changes when RubyGems
is released.

Upon release:
* ../blog.rubygems.org is cloned
* A blog post is generated based on History.txt
* An editor is opened with the generated post for verification
* The blog post is committed
* The commit is pushed