feat(config, css): resolve packages exporting non js files

lib/app/App.vue

@@ -8,7 +8,7 @@
 <script>
 <% if (loading) { %>import NuxtLoading from '<%= (typeof loading === "string" ? loading : "./components/nuxt-loading.vue") %>'<% } %>
 <% css.forEach(function (c) { %>
-import '<%= wp(c.src || c) %>'
+import '<%= relativeToBuild(resolvePath(c.src || c)) %>'
 <% }) %>
 
 let layouts = {

lib/builder/builder.js

@@ -242,6 +242,7 @@ export default class Builder extends Tapable {
           hash,
           r,
           wp,
+          resolvePath: this.nuxt.resolvePath.bind(this.nuxt),
           relativeToBuild: this.relativeToBuild
         }
       })

lib/core/nuxt.js

@@ -5,6 +5,7 @@ import Renderer from './renderer'
 import Options from './options'
 import Debug from 'debug'
 import enableDestroy from 'server-destroy'
+import Module from 'module'
 import { join, resolve } from 'path'
 
 const debug = Debug('nuxt:')
@@ -16,6 +17,9 @@ export default class Nuxt extends Tapable {
 
     this.options = Options(_options)
 
+    // Paths for resolving requires from `rootDir`
+    this.nodeModulePaths = Module._nodeModulePaths(this.options.rootDir)
+
     this.initialized = false
     this.errorHandler = this.errorHandler.bind(this)
 
@@ -101,7 +105,7 @@ export default class Nuxt extends Tapable {
   resolvePath (path) {
     // Try to resolve using NPM resolve path first
     try {
-      let resolvedPath = require.resolve(path)
+      let resolvedPath = Module._resolveFilename(path, { paths: this.nodeModulePaths })
       return resolvedPath
     } catch (e) {
       // Just continue