Revert "Use jekyll-assets"

This reverts commit 9062937951.

_config.yml

@@ -3,7 +3,7 @@ description: "Liquid is a template language and accompanying rendering engine. I
 repository: https://github.com/Shopify/liquid
 
 # Build settings
-# baseurl:                /liquid # the subpath of your site, e.g. /blog/
+baseurl:                /liquid # the subpath of your site, e.g. /blog/
 url:                    http://liquidmarkup.org # the base hostname & protocol for your site
 markdown:               redcarpet
 redcarpet:
@@ -25,12 +25,3 @@ defaults:
       path: "" # an empty string here means all files in the project
     values:
       layout: default
-
-# Plugins
-gems:
-  - jekyll-assets
-
-## jekyll-assets
-sources:
-  - _assets/css
-  - _assets/images