Use comment instead of directive for ASDF magic
Update file_layout.rst

make -> made
Merge pull request #34 from mdboom/use-asdf-comment

Use comment instead of directive for ASDF magic
Update tree.rst

Remove redundant "schema"--add clarification.
Add reference file suite
Merge pull request #39 from mdboom/make-reference-files

Add reference file suite
Finer grained datatype reference files