Add note about `plugins` name change

_config.yml

@@ -30,7 +30,7 @@ logo: # path of site logo, e.g. "/assets/images/logo.png"
 # Build settings
 markdown: kramdown
 theme: jekyll-theme-basically-basic
-plugins:
+plugins: # previsously gems
   - jekyll-feed
   - jekyll-seo-tag
   - jekyll-sitemap

docs/_config.yml

@@ -53,7 +53,7 @@ permalink: /:categories/:title/
 timezone: America/New_York # http://en.wikipedia.org/wiki/List_of_tz_database_time_zones
 
 # Plugins
-plugins:
+plugins: # previously gems
   - jekyll-feed
   - jekyll-seo-tag
   - jekyll-sitemap

example/_config.yml

@@ -34,7 +34,7 @@ liquid:
 # Build settings
 markdown: kramdown
 theme: jekyll-theme-basically-basic
-plugins:
+plugins: # previously gems
   - jekyll-feed
   - jekyll-seo-tag
   - jekyll-sitemap