Added version flag to CLI

lib/cli.js

@@ -7,6 +7,7 @@ var watch = require('node-watch'),
 
 var yargs = require('yargs')
   .usage('Compile .scss files with node-sass.\nUsage: $0 [options] <input.scss> [<output.css>]')
+  .version(require('../package.json').version, 'version').alias('version', 'V')
   .options('output-style', {
     describe: 'CSS output style (nested|expanded|compact|compressed)',
     'default': 'nested'