Fix name of CommentNode file

This was accidentally named `comment.rb` instead of `comment_node.rb`,
so the `NodeTransformer` couldn't find it.

It was also missing the `Tree` from its module namespace, so add that as
well.

Change-Id: Id41783ef103a9171495cd7b70862d8a40626ecda
Reviewed-on: http://gerrit.causes.com/42574
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>
Add missing superclasses to Nodes

The CommentNode and DoctypeNode were missing their superclasses, so
initializing them wouldn't work.

Change-Id: I60ab0906bd56b6ca61027c41ee6e1200de520f00
Reviewed-on: http://gerrit.causes.com/42575
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>
Fix ClassAttributeWithStaticValue crash on method call attributes

This linter would crash with a parse error if the user assigned
attribute via a method call, e.g.

    %tag{ some_method_call }

The solution is to catch "unexpected token tRCURLY" and ignore it in
this case.

We could also change the code to be wrapped inside a dummy merge, e.g.

   {}.merge( ... )

...but until this becomes more of an issue, we'll keep it simple.

Change-Id: I43e79f0de317404eb7b5b4b5c071757579455376
Reviewed-on: http://gerrit.causes.com/42576
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>