extracts model-tenantizing code so extensions can reuse
refactors the way we tenantize models.  updates spree_auth_devise
lowers case on a test to match what's shown in the HTML
fixes typo in spec
upgrades tests to use i18n for 'logged in as'.  updates spree_auth_devise until gem version issue is resolved
Merge pull request #1 from jsqu99/master

Adds Tenantizable