Lockdown select2-rails temporarily.
Update select2-rails now that it has been fixed.
Add changelog entry for #3481

Conflicts:
	core/CHANGELOG.md
Add another migration to link existing line items with their tax categories

Related to #3481
Remove deprecated -moz-border-radius clause (deprecated in Firefox 13)
Fix styling of select2's droparrow
Put checkboxes before descriptions in shipping methods form

Fixes #3483
Fix IE8 compatibility issues with checkout.js and products.js

IE8 has a weird bug where function definitions outside of a ready statement were not being acknowledged