Migrate to Meteor Blaze

Replace Handlebars.registerHelper with UI.registerHelper
Remove deprecated/unneeded .preserve
Template._loginButtons() no longer supported, so just return Template._loginButtons - which means {{> loginButtons}} is now needed to use helper
Update smart.json so that package can be released until parent package supports Blaze
apply original smart.json
use 0.3.0-1 for consistency with accounts-ui-bootstrap-3-blaze. Blaze support needs major version number