src: add support for character devices
doc: fix usePolling default values

- It uses polling by default in both Linux and OS X.
Merge pull request #142 from santigimeno/character_devices

src: add support for character devices
Merge pull request #143 from santigimeno/fix_README

doc: fix usePolling default values
Merge branch 'master' of https://github.com/paulmillr/chokidar