message: replace Calendar div wrapper with Fragment
diff: -import React, { Component } from 'react';
  +import React, { Component, Fragment } from 'react';
  import PropTypes from 'prop-types';
  import { withStyles, IconButton } from 'material-ui';
  @@ -135,7 +135,7 @@ export class Calendar extends Component {
  const { classes, utils } = this.props;
  return (
  - <div className={classes.container}>
  + <Fragment>
  <CalendarHeader
  currentMonth={currentMonth}
  onMonthChange={this.handleChangeMonth}
  @@ -147,7 +147,7 @@ export class Calendar extends Component {
  <div className={classes.calendar}>
  {this.renderWeeks()}
  </div>
  - </div>
  + </Fragment>
  );
  }
  }
  