Add producer account image defaults

  * add `defaultClass` attribute to `prxImg` directive
    which adds the class if no img url is provided
  * add `default` attribute to `prxImg` directive
    which sets the img src if no img url is provided
  * allow failing to get an account image
  * add a default account image which is applied via a class
make karma builds sane
Merge branch 'master' into feat/default_account_images
copy files because angular templates is broken
Merge pull request #53 from PRX/feat/default_account_images

add default account images