Link to the source code from the homepage

[afeld]

http://sparklines.rubyforge.org/ doesn't seem to link to this repository, which makes it harder to find. Thanks!

/cc @Willooz

[topfunky]

Hmm. I forget how to even publish to Rubyforge and the main page is down. http://rubyforge.org

[afeld]

Maybe just link to this page instead, which is auto-generated from the latest gem?

http://www.rubydoc.info/gems/sparklines