Merge branch 'release/0.9' into develop
Added link from product jars to inventory by product.  Fixes #20.

I've added the cross-link from product to inventory.
Changed 'similar products' to only display active products with jars in stock.  Fixes #19.

Changed references to Product.active to Product.instock.filter(is_active=True).
Merge branch 'hotfix/0.9.1' into develop
Minor documentation change.
Merge branch 'hotfix/0.9.2' into develop