getRoles () {
    return new Promise((resolve, reject) => {
      Vue.axios.get('api/user/roles').then((response) => {
        const roles = Vue.filter('parseRoles')(response.data.roles);
        return resolve(roles);
      }).catch((err) => {
        return reject(err);
      });
    });
  }
Gets roles available to users
@returns {Promise} Promise A promise object that signals the completion
                           or rejection of the request.