update qiime.org landing page

[gregcaporaso]

I've seen several instances lately of people being referred to qiime.org when they should be referred to qiime2.org. This update provides a simple page that (manually) redirects the user to qiime2.org, but gives them an option to still access the old qiime.org page.

Preview of new index page:

[wasade]

Just a small question otherwise :+1:

[gregcaporaso]

Thanks @wasade!