fix Cannot read property 'removeListener' of undefined

[modosc]

right now >1.3.0 is totally broken for me, i get this error:

     TypeError: Cannot read property 'removeListener' of undefined
      at Mql.dispose (node_modules/react-responsive/dist/react-responsive.js:1051:9)
      at MediaQuery.updateQuery (node_modules/react-responsive/dist/react-responsive.js:176:20)
      at MediaQuery.componentWillReceiveProps (node_modules/react-responsive/dist/react-responsive.js:151:13)
      at node_modules/react-dom/lib/ReactCompositeComponent.js:610:23

this fix also depends on ncochard/matchmediaquery#1 - until that's merged and used here this test will continue to fail (i tested this locally though and combined together both seem to fix the problem)

[modosc]

ok - this should be good to go now.