Adds basic rewrite using shelve module.
Updates readme.
Makes all tests work.
Fixes close() method.
Returns keys as bytes/str depending on serialization setting.
Updates description for rewrite.
Makes Python 3 documentation default for doc links.
Updates package setup metadata.
Removes old documentation.
Formats change log for new docs.
Updates documentation for rewrite
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fcache rewrite.
Merge branch 'feature/rewrite' into develop