Add node_modules back to NODE_PATH

This is required until all packages are migrated to include their
dependencies in package.json instead of requiring other modules directly
from core.

This allows apm linking to still working while packages are migrated.

src/atom-window.coffee

@@ -42,7 +42,12 @@ class AtomWindow
     @openPath(pathToOpen, initialLine)
 
   setupNodePath: (resourcePath) ->
-    process.env['NODE_PATH'] = path.resolve(resourcePath, 'exports')
+    paths = [
+      'exports'
+      'node_modules'
+    ]
+    paths = paths.map (relativePath) -> path.resolve(resourcePath, relativePath)
+    process.env['NODE_PATH'] = paths.join path.delimiter
 
   getInitialPath: ->
     @browserWindow.loadSettings.initialPath