Remove serialization.
Remove instantiation with items.
Change access methods

Renamed:
insert -> add
length -> size

Added:
get, aliased as []
Add find-like methods for deleting items.
Change methods for retrieving items.
Remove examples from inline documentation.
Rewrite condition matching for queries

Using instance methods instead of blocks simplifies the code and improves performance by about 30 %.
Rewrite initialization.
Update README and RDoc options.
Update Gemspec.
Add refinement for arrays.