Stop testing with backwards-compatible site config (#211)

Merge pull request 211

Author: ashmaroli

.travis.yml

@@ -12,7 +12,7 @@ matrix:
       rvm: 2.5.3
       env: GH_PAGES=true
     - rvm: *latest_ruby
-      env: JEKYLL_VERSION=">= 4.0.0.pre.alpha1"
+      env: JEKYLL_VERSION="~> 4.0"
 
 before_install:
 - gem update --system

spec/spec_helper.rb

@@ -42,15 +42,15 @@ def config
         "authors"  => {},
       },
       "url"         => "http://jekyllrb.com",
-      "gems"        => [
+      "plugins"     => [
         "jekyll-redirect-from",
         "jekyll-sitemap",
       ],
       "defaults"    => [{
         "scope"  => { "path" => "" },
         "values" => { "layout" => "layout" },
       }]
-    ).backwards_compatibilize
+    )
   end
 
   def site