bump version 2.4.0

2.3.0: expose env to template data

2.2.3: root will now be resolved to srcpath instead of destpath

2.2.2: removes package-lock.json

2.2.1: fixes default user group

2.2.0: a new option --upstream is introduced to ngx down

2.1.3: fixes DEFAULT_ENV

2.1.1: fs-promise -> fs-extra

2.1.1: cli user will override preset

2.1.0: ngx -v will also print ngx version