Workaround for intermittent crashing (bug
https://github.com/paulmillr/chokidar/issues/133)
Updated README.
Allowing to set the extension root dir (`EXTENSION_ROOT_DIR` env var).

Conflicts:
	package.json
Fixed test config env var name.
Added node minimal version to `package.json`.
Added node minimal version to circle.yml.
Updated README.
Merge pull request #8 from kitt-browser/fix/enoent-crash

Workaround for intermittent crashing (bug