   {name: 'Outdoor', head: true},
        {name: 'Skydiving', tag: '1 spot left', group: 'Outdoor'},
        ...
    ]
-->

<link rel="import" href="/components/iron-flex-layout/iron-flex-layout-classes.html">
<link rel="import" href="/components/iron-form-element-behavior/iron-form-element-behavior.html">
<link rel="import" href="/components/iron-validatable-behavior/iron-validatable-behavior.html">
<link rel="import" href="/components/paper-input/paper-input.html">
<link rel="import" href="/components/pap