Fixed Ctrl+Backspace word delete on Linux
Fixed Ctrl+Backspace word delete on Linux

closes #634
- toggle <kbd>Ctrl+Backspace</kbd> behaviour based on not being on Mac rather than checking for Windows explicitly

bustle/mobiledoc-kit,bustlelabs/content-kit-editor,YoranBrondsema/mobiledoc-kit,YoranBrondsema/mobiledoc-kit,bustlelabs/mobiledoc-kit,bustlelabs/content-kit-editor,bustle/mobiledoc-kit,bustlelabs/content-kit-editor,mixonic/content-kit-editor,bustle/mobiledoc-kit,YoranBrondsema/mobiledoc-kit,bustle/mobiledoc-kit,mixonic/content-kit-editor,bustlelabs/mobiledoc-kit,bustlelabs/mobiledoc-kit,mixonic/content-kit-editor