fix(isFastboot): Fix isFastboot checkt
fix(isFastboot): Fix isFastboot checkt

For some reason the fastboot check with typeof FastBoot !== 'undefined' didnt work for me and
other users see: issue #5 (https://github.com/runspired/ember-run-raf/issues/5)

There should be no breaking changes

runspired/ember-run-raf,runspired/ember-run-raf