Remove duplicate rake task and enable metadata.json linting

The :validate task is already provided by
puppetlabs_spec_helper/rake_tasks and would check files twice.

The metadata.json linting is just good form.

Gemfile

@@ -17,6 +17,7 @@ group :development, :unit_tests do
   gem 'mocha',                   :require => false
   gem 'puppetlabs_spec_helper',  :require => false
   gem 'puppet-lint',             :require => false
+  gem 'metadata-json-lint',      :require => false
   gem 'pry',                     :require => false
   gem 'simplecov',               :require => false
 end

Rakefile

@@ -4,15 +4,3 @@ require 'puppet-lint/tasks/puppet-lint'
 PuppetLint.configuration.send('disable_80chars')
 PuppetLint.configuration.ignore_paths = ["spec/**/*.pp", "pkg/**/*.pp"]
 
-desc "Validate manifests, templates, and ruby files in lib."
-task :validate do
-  Dir['manifests/**/*.pp'].each do |manifest|
-    sh "puppet parser validate --noop #{manifest}"
-  end
-  Dir['lib/**/*.rb'].each do |lib_file|
-    sh "ruby -c #{lib_file}"
-  end
-  Dir['templates/**/*.erb'].each do |template|
-    sh "erb -P -x -T '-' #{template} | ruby -c"
-  end
-end