fix boolean params

lib/cli.js

@@ -15,7 +15,8 @@ var optimist = require('optimist')
     'default': 'none'
   })
   .options('source-map', {
-    describe: 'Emit source map'
+    describe: 'Emit source map',
+    type: 'boolean'
   })
   .options('include-path', {
     describe: 'Path to look for @import-ed files',
@@ -31,14 +32,16 @@ var optimist = require('optimist')
   })
   .options('watch', {
     describe: 'Watch a directory or file',
-    alias: 'w'
+    alias: 'w',
+    type: 'boolean'
   })
   .options('output', {
     describe: 'Output css file',
     alias: 'o'
   })
   .options('stdout', {
-    describe: 'Print the resulting CSS to stdout'
+    describe: 'Print the resulting CSS to stdout',
+    type: 'boolean'
   })
   .options('help', {
     describe: 'Print usage info',