Add tests for importing sub-files/directories from npm packages (#337)

Author: oleersoy

test/fixtures/resolve-npm-subpackages.css

@@ -0,0 +1,2 @@
+@import "modularized-css/foo";
+@import "modularized-css/foo/boo/boomod.css";

test/fixtures/resolve-npm-subpackages.expected.css

@@ -0,0 +1,2 @@
+.i-pity-the-foo{}
+.i-pity-the-boo{}

test/node_modules/modularized-css/foo/boo/boomod.css

@@ -51,6 +51,14 @@ test(
   { from: "test/fixtures/imports/foo.css" }
 )
 
+test(
+  "should be able to consume npm sub packages",
+  checkFixture,
+  "resolve-npm-subpackages",
+  { path: null },
+  { from: "test/fixtures/imports/foo.css" }
+)
+
 test(
   "should be able to consume modules from custom modules directories",
   checkFixture,