add medium image size to product catalog response
Merge pull request #7 from HeroInt/add-paperclip-image-size

add medium image size to product catalog response
index images only if present
Merge pull request #8 from HeroInt/bugfix/fix-image-indexing

index images only if present
Merge branch 'master' into feature/add-mobile-images

Conflicts:
	lib/spree_catalog_solr/utils.rb