Rough port to a Chrome packaged app.
Refinement of the app.

Added more fileSystem perms.
Moved toasts to their own area in meme-app.
Scaffold checking for directory storing memes.
Fixed image saving and dialogs.
Image saving with file chooser.

Suggested filename based on meme macro.
Merge pull request #1 from jwill/chrome-packaged-app

Merge Chrome packaged app branch.