add JavaScript-MD5 to bower.json; import it in Brocfile and declare as global in .jshintrc
add components/gravatar-image, creates an img tag with src set to gravatar url using md5 hash of user email
user/index.hbs, use {{gravatar-image}} to display user profile pic
config/environment.js, add content security policy to permit img src from gravatar
add tests/../gravatar-image-test