Errata of the Ember.js book https://leanpub.com/ember-cli-101.
On page 49 (book version downloaded from 3/30/15 email update), the following line needs to be added to the Brocfile.js instructions for Picnic css dependency:
app.import('bower_components/picnic/releases/plugins.min.css');
This is needed for the "-header.hbs" <nav>
UI element (introduced on page 51) to get its Picnic styling which is not included in the plain picnic.css but is included in Picnic's plugins.css
[Related to Issue: Page 49: Need to add Picnic's "plugins.min.css" to Brocfile.js #193] (abuiles#193)