Bump to 2.1.0.beta
improve tumblr share: add name & description

* Share uses title and description of product
* Opens in new window when javascript enabled

Fixes #19
Use admin/spree_backend.css

admin/spree_frontend.css was removed by spree commit:
56d94de4896198464d3cfb487f8b4b3d7c84d81d

app/assets/stylesheets/admin/spree_social_products.css: Update to reflect the change

Fixes #20
Depend on 2.2.0.beta
Fix asset paths in 2-2-stable
showing configurations sidebar on social sharing settings area
Use spree_core 2.3.0.beta

Fixes #26
update to 2-0-stable compatible
update spree social for facebook to html5 and app configurations for stable-2-0