fixed type, added cookbook

Accidentally used idempotent instead of associative. Oops.
Fix dict-style access, recursive Sequences

Fixes for issues 4, 5.

setting of attributes was double-wrapping dicts as AttrDicts.
Sequences are now recursed in such a way that they maintain their type (when possible)
added ignore file finally
incremented version
updated CHANGES file
Merge pull request #6 from bcj/v0.2.1

V0.2.1