Do validation and warning of button theme

[notmessenger]

https://github.com/softlayer/sl-ember-components/blob/master/addon/components/sl-button.js#L259-L261

/**
 * Theme values
 *
 * @memberof module:addon/components/ef-button
 * @enum {String}
 * @property {String} DANGER 'danger'
 * @property {String} INFO 'info'
 * @property {String} LINK 'link'
 * @property {String} PRIMARY 'primary'
 * @property {String} SECONDARY 'secondary'
 * @property {String} SUCCESS 'success'
 * @property {String} WARNING 'warning'
 */
export const Theme = Object.freeze({
  DANGER: 'danger',
  INFO: 'info',
  LINK: 'link',
  PRIMARY: 'primary',
  SECONDARY: 'secondary',
  SUCCESS: 'success',
  WARNING: 'warning'
});