Add puppet linters (#183)

* Start adding Puppet linters

* Use the correct output stream for puppet parser

* Finish Puppet and puppet-lint linters

* Add Puppet information to documentation

ale_linters/puppet/puppetlint.vim

@@ -0,0 +1,8 @@
+" Author: Alexander Olofsson <alexander.olofsson@liu.se>
+
+call ale#linter#Define('puppet', {
+\   'name': 'puppetlint',
+\   'executable': 'puppet-lint',
+\   'command': g:ale#util#stdin_wrapper . ' .pp puppet-lint --no-autoloader_layout-check --log-format "-:%{line}:%{column}: %{kind}: [%{check}] %{message}"',
+\   'callback': 'ale#handlers#HandleGCCFormat',
+\})