Add -v flag to print the version

src/main.coffee

@@ -62,9 +62,15 @@ parseCommandLine = ->
   options.alias('n', 'new-window').boolean('n').describe('n', 'Open a new window.')
   options.alias('t', 'test').boolean('t').describe('t', 'Run the Atom specs and exit with error code on failures.')
   options.alias('w', 'wait').boolean('w').describe('w', 'Wait for window to be closed before returning.')
+  options.alias('v', 'version').boolean('v').describe('v', 'Print the version.')
   args = options.argv
+
   if args.h
-    options.showHelp()
+    process.stdout.write(options.help())
+    process.exit(0)
+
+  if args.v
+    process.stdout.write("#{version}\n")
     process.exit(0)
 
   executedFrom = args['executed-from']