README.md: fix link to puppet-lint (#283)

README.md

@@ -403,5 +403,5 @@ Please report bugs and feature request using [GitHub issue
 tracker](https://github.com/camptocamp/puppet-postfix/issues).
 
 For pull requests, it is very much appreciated to check your Puppet manifest
-with [puppet-lint](https://github.com/camptocamp/puppet-postfix/issues) to follow the recommended Puppet style guidelines from the
+with [puppet-lint](http://puppet-lint.com/) to follow the recommended Puppet style guidelines from the
 [Puppet Labs style guide](http://docs.puppetlabs.com/guides/style_guide.html).