Spree 1.1 compatibility
Removed Gemfile.lock. Should not exists for gems / extensions
Added support for spree_digital's multi-attachment on variants; improving formatting

* List multiple links for a single variant that has multiple digital files
* Improving formatting / UX
Fixing some bugs with the shipping notification email and improving the formatting
Updated to premailer-rails 1.2. Removed &nbsp; from email template
Added digital links to shipping notification

This is a bit better for UX. If the user looks at their
shipping notification for their shipped physical items
they don't have to look at another for their digital links.
Fixing issue with cancellation email formatting
Shipment confirmation only contains items shipped within that shipment.

Reference: https://github.com/spree/spree/pull/1867
Documentation update
Loosening dependencies for > 1.1 compat
Minor documentation improvement
Removing custom time definition.

I think this was overriding some core rails format, which was causing
time formatting issues (things were being marked as Feb 10, not sure why).
Stricter premailer versioning

Premailer changed their gem name which caused some issues.
We'll update to the latest version of premailer later, this is just a stopgap
Tests running; not passing yet