Updated dependencies notation to be more compatible with old nodes

- removed `engine` - it's really useless and not recommended
- replaced `^` with `~` - only third number of semver is allowed to change safely for automatic updates. `^` is not supported by older npm.

We now use `csswring` in [mincer](https://github.com/nodeca/mincer), and really need backward compatibility.
Merge pull request #1 from puzrin/patch-1

Updated dependencies notation to be more compatible with old nodes