Remove warnings when running jekyll, closeselixir-lang#1035

Author: José Valim

Gemfile

@@ -1,3 +1,4 @@
 source'https://rubygems.org'
 
 gem'github-pages'
+gem'json','>= 2.0.0'

Gemfile.lock

@@ -153,6 +153,7 @@ GEM
 gemoji (~>3.0)
 html-pipeline (~>2.2)
 jekyll (>=3.0)
+json (2.1.0)
 kramdown (1.13.2)
 liquid (4.0.0)
 listen (3.0.6)
@@ -199,6 +200,7 @@ PLATFORMS
 
 DEPENDENCIES
 github-pages
+json (>=2.0.0)
 
 BUNDLED WITH
 1.15.3

_config.yml

@@ -4,7 +4,7 @@ kramdown:
 input: GFM
 hard_wrap: false
 repository: elixir-lang/elixir-lang.github.com
-gems:
+plugins:
  - jemoji
  - jekyll-sitemap
  - jekyll-redirect-from