Add grune-yaml skeleton.
Add yaml specializations for non_terminal.
Add YAML emit/parse test skeleton.
Add infrastructure for emit tests.
Fixup the 'check' target.
Implement symbol emitting
Actually test things in the generation tests.
Add sequence YAML tests.
Add sequence_list YAML tests.
Merge branch 'master' into yaml
Add production YAML emit.
Remove diff tests since yaml-cpp's key ordering is a lot less stable than I expected.
Clean up test infrastructure
Merge branch 'master' into yaml
Merge branch 'master' into yaml
Add grammar YAML emit
Don't require additional headers for sample grammars
Add sample yaml file generator
Simplify YAML format a little.