Get the version from the package.json and inject it into version.js, when building crafty.js file.
Merge pull request #587 from kevinsimper/injectVersion

- Get the version from the package.json and inject it into version.js
- Use version.js to return version number in core.js
Fix package.json

See https://github.com/craftyjs/Crafty/commit/3c245adc47b299c34b57b865f3bd004ab1be0978#commitcomment-4454656
Merge pull request #588 from potomak/feature/fix-package

Fix package.json