Moved npm dependencies to devDependencies

[ProLoser]

Not sure how knowledgable you are on npm design patterns.

I installed this package using npm install nwcell/ics.js but it came with a lot of stuff I don't need in production. Obviously I don't need grunt or bower or the libraries you hard-coded into the distribution files in order to consume your library. I only need those dependencies if I want to develop your package itself. Therefore I've moved those dependencies down.

If you want to be consumed by node but not hard-code the third party packages, I would keep file-saver as a production dependency and use something like rollup or browserify or something to distribute.