Fix error message in doc_builder, don't close non existant file handle
Warn on non-categorized doc blocks, add file name to skipped doc block warnings
Warn when parent block could not be found
Error out when a page has no category
Default name to title with underscores and update is_valid
Update tests for new validation and method signatures
Merge pull request #83 from jdcantrell/require-category

Require category in document blocks