message: Change the menu toggle to a checkbox
diff: <link rel='import' href='../bower_components/polymer/polymer.html'>
  <link rel='import' href='../bower_components/paper-button/paper-button.html'>
  <link rel='import' href='../bower_components/paper-input/paper-input.html'>
  -<link rel='import' href='../bower_components/paper-toggle-button/paper-toggle-button.html'>
  +<link rel='import' href='../bower_components/paper-checkbox/paper-checkbox.html'>
  <link rel='import' href='./cloud-install-styles.html'>
  <link rel='import' href='./outline-iconset.html'>
  .clickable {
  cursor: pointer;
  }
  - paper-toggle-button {
  - --paper-toggle-button-checked-bar-color: var(--primary-green);
  - --paper-toggle-button-checked-button-color: var(--primary-green);
  - --paper-toggle-button-checked-ink-color: var(--primary-green);
  - --paper-toggle-button-unchecked-bar-color: var(--dark-gray);
  + paper-checkbox {
  + /* We want the ink to be the color we're going to, not coming from */
  + --paper-checkbox-checked-color: var(--primary-green);
  + --paper-checkbox-checked-ink-color: var(--dark-gray);
  + --paper-checkbox-unchecked-color: var(--dark-gray);
  + --paper-checkbox-unchecked-ink-color: var(--primary-green);
  }
  paper-input {
  /* Removes extra padding added by children of paper-input */
  <div>
  <div id="metricsHeader">
  <h3>Share anonymous metrics</h3>
  - <paper-toggle-button id="metricsToggle" checked="{{metricsEnabled}}"></paper-toggle-button>
  + <paper-checkbox id="metricsCheckbox" checked="{{metricsEnabled}}"></paper-checkbox>
  </div>
  <p>Share anonymized metrics to help improve the reliability and performance of Outline, for you and for those you share your server with. <a class="link" href="https://s3.amazonaws.com/outline-vpn/index.html#/en/support/dataCollection">Learn more</a>.</p>
  </div>
  