Warn on unrecognised puppet-strings tags

[alexjfisher]

This quite possibly belongs in a different plugin, but some of the issues I've come across include...

Capitalisation of tags. eg.

# @Summary This class installs foo
#

Someone meant to use @summary but used @profile instead.

# @profile This profile installs foo
#

Using the name of a parameter as a tag instead of @param

# @ensure Whether to install or remove foo

[ekohl]

It doesn't feel appropriate here. Perhaps we need a new puppet-lint-puppet-strings that parses docs and warns on the errors it generates?