0.9.0 beta 6

Refactoring:

• Move validate_* functions into extras_* instead
• Use Dynamic for the type of .dynamic
• Reformat single quotes to double quotes to match packaging
• Produce standard Python repr style in error messages

Fixes:

• Improve locking for just metadata fields

Docs:

• Include extra badge in readme
• Rework docs, include README and more classes
• Changelog is now in markdown