lib/psych.rb: Flesh out documentation.
* lib/psych/core_ext/exception.rb: Handle instance variables for deserialized Exception.
* lib/psych/core_ext/struct.rb: Handle instance variables for deserialized Struct.
* lib/psych/deprecated.rb: Use legacy tag.
Use array of Tag in Schema instead of Hash os String.
Presedence of tags is last first.
* lib/test/psych.rb: Add FIXME note about issue with to_yaml_properties.
Remove test_anon_struct_legacy test, it is no longer valid.
Skip test, no longer support old YAML 1.0 tag prefixes.
Fix deprecated tests.