Remove unneeded dependencies

puppetlabs_spec_helper handles these dependencies for us.

Gemfile

@@ -1,10 +1,8 @@
 source ENV['GEM_SOURCE'] || "https://rubygems.org"
 
 group :development, :unit_tests do
-  gem 'rake',                    :require => false
   gem 'rspec-core', '3.1.7',     :require => false
   gem 'puppetlabs_spec_helper',  :require => false
-  gem 'puppet-lint',             :require => false
   gem 'simplecov',               :require => false
   gem 'puppet_facts',            :require => false
   gem 'json',                    :require => false