Adding Gemfile depend and instructions

Gemfile

@@ -0,0 +1,5 @@
+source "https://rubygems.org"
+
+gem 'json'
+gem 'hash-joiner'
+gem 'open-uri-cached'

readme.md

@@ -2,6 +2,13 @@
 
 Add this file to `_plugins` in the root of your Jekyll site.
 
+Add dependencies from Gemfile to your jekyll site's Gemfile
+
+# Run
+`bundle install`
+`jekyll build`
+`jekyll serve`
+
 # Configure
 
 This plugin reads settings from the `_config.yml` file. Add settings as attributes or an array of attributes for multiple files.