Fixed Rakefile to prevent linter to check files under vendor

Author: vfoucault

Diff for: Rakefile

@@ -9,7 +9,7 @@ end
 
 PuppetLint.configuration.send('disable_80chars')
 PuppetLint.configuration.relative = true
-PuppetLint.configuration.ignore_paths = ['spec/**/*.pp', 'pkg/**/*.pp']
+PuppetLint.configuration.ignore_paths = ['spec/**/*.pp', 'pkg/**/*.pp', 'vendor/**/**']
 
 desc 'Validate manifests, templates, and ruby files'