Update URL & spelling in index.rst

The documentation under http://loci.wisc.edu/software/bio-formats
now directs to pages under http://www.openmicroscopy.org/site/support/bio-formats
and the over all landing page is http://www.openmicroscopy.org/site/products/bio-formats.
Merge pull request #1 from joshmoore/patch-1

Update URL & spelling in index.rst