Allow imports from node modules with default install (#11)

Author: Jamie Hill

lib/install/sass/install.rb

@@ -3,4 +3,4 @@
 run "yarn add sass"
 
 say "Add build:css script"
-run %(npm set-script build:css "sass ./app/assets/stylesheets/application.sass.scss ./app/assets/builds/application.css --no-source-map")
+run %(npm set-script build:css "sass ./app/assets/stylesheets/application.sass.scss ./app/assets/builds/application.css --no-source-map --load-path=node_modules")