Remove IE9 and 10 in ENVIRONMENTS.md (#342)
Remove IE9 and 10 in ENVIRONMENTS.md (#342)

https://github.com/firebase/firebase-js-sdk/issues/341
FirebasePrivate/firebase-js-sdk-1,FirebasePrivate/firebase-js-sdk-1,jsayol/firebase-js-sdk,jsayol/firebase-js-sdk,FirebasePrivate/firebase-js-sdk-1,FirebasePrivate/firebase-js-sdk-1,jsayol/firebase-js-sdk,jsayol/firebase-js-sdk,FirebasePrivate/firebase-js-sdk-1,jsayol/firebase-js-sdk