Fix nokogiri version dependency for puppet-blacksmith. (#298)

Author: ardrigh

.travis.yml

@@ -1,6 +1,7 @@
 language: ruby
 before_install: rm -f Gemfile.lock
 sudo: false
+bundler_args: --full-index
 cache: bundler
 rvm:
   - 2.0.0

Gemfile

@@ -16,5 +16,6 @@ group :development do
   gem "beaker", '2.51.0'
   gem "beaker-rspec"
   gem "puppet-blacksmith"
+  gem "nokogiri", "~> 1.6.0"
   gem "guard-rake"
 end