fix(Dropdown): Doesn't render sub-menus

[maulberto3]

Steps to Reproduce

import React from 'react'
import { Dropdown, Icon } from 'semantic-ui-react'

const DropdownExampleMenuDirection = () => (
  <Dropdown text='Menu' floating labeled button className='icon'>
    <Dropdown.Menu>
      <Dropdown.Item>
        <Icon name='left dropdown' />
        <span className='text'>Left</span>
        <Dropdown.Menu className='left'>
          <Dropdown.Item>1</Dropdown.Item>
          <Dropdown.Item>2</Dropdown.Item>
          <Dropdown.Item>3</Dropdown.Item>
        </Dropdown.Menu>
      </Dropdown.Item>
      <Dropdown.Item>
        <Icon name='dropdown' />
        <span className='text'>Right</span>
        <Dropdown.Menu className='right'>
          <Dropdown.Item>1</Dropdown.Item>
          <Dropdown.Item>2</Dropdown.Item>
          <Dropdown.Item>3</Dropdown.Item>
        </Dropdown.Menu>
      </Dropdown.Item>
    </Dropdown.Menu>
  </Dropdown>
)

Expected
The Dropdown should render sub-menus ("1", "2", "3").

Result
The Dropdown only render main menus ("left", "right").

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[layershifter]

Duplicate, see #1724 for more details.

[maulberto3]

I just saw the nested dropdowns not supported...

[maulberto3]

But then again, I see above that the:
"Pointing
A dropdown can be formatted so that its menu is pointing."
dropdown is working with nested dropdowns.
So it is functional right?