How to use plugin as a gem? Have Sloution?

I use following command for installing thinking-sphinx plugin but I got
empty folder.

F:\RubyProjects\SphinxTest>ruby script/plugin install
git://github.com/freelancing-god/thinking-sphinx.git

Then I download thinking-sphinx from

and install it as a gem , as following

C:\Think-Sphinx>gem build thinking-sphinx.gemspec
Successfully built RubyGem
Name: thinking-sphinx
Version: 1.1.6
File: thinking-sphinx-1.1.6.gem

C:\Think-Sphinx>gem install thinking-sphinx-1.1.6.gem
Successfully installed thinking-sphinx-1.1.6
1 gem installed
Installing ri documentation for thinking-sphinx-1.1.6…
Installing RDoc documentation for thinking-sphinx-1.1.6…

Now when I run rake task. I got following error.

F:\RubyProjects\SphinxTest>rake thinking-sphinx:index

(in F:/RubyProjects/SphinxTest)
rake aborted!
Don’t know how to build task ‘thinking-sphinx:index’

(See full trace by running task with --trace)

Why this is not working?
How to solve this issue? If i want to use plugin as a gem for rails
application how i use it?

Thanks,

Vikas