Add the ability to specify other postcss options (#99)

* Add the ability to specify other postcss options

* Fixed usage of postcss

lib/style-rewriter.js

@@ -45,9 +45,16 @@ module.exports = function (id, css, scoped, options) {
   if (val) {
     return Promise.resolve(val)
   } else {
-    var plugins = options.postcss
-      ? options.postcss.slice()
-      : []
+    var plugins = []
+    var opts = {}
+
+    if (options.postcss instanceof Array) {
+      plugins = options.postcss.slice()
+    } else if (options.postcss instanceof Object) {
+      plugins = options.postcss.plugins || []
+      opts = options.postcss.options
+    }
+
     // scoped css rewrite
     if (scoped) {
       plugins.push(addId)
@@ -60,10 +67,11 @@ module.exports = function (id, css, scoped, options) {
     }
     currentId = id
     return postcss(plugins)
-      .process(css)
+      .process(css, opts)
       .then(function (res) {
         cache.set(key, res.css)
         return res.css
       })
   }
 }
+