v1.4.0

• Rename keep_counts to keep_counts_ge. Add le, lt, gt, eq, and ne variants.
• Add count_subset evaluation that counts how many times the right side is contained in the left.
• Add ImplicitConversionError as subclass of TypeError.
• Add binary multiset operators to Deck.
• Add modulo_counts / % operation on multisets.
• Rebind generators and evaluate when fully bound non-generator expressions are given to an evaluator.
• Fix Symbols intersection.
• Fix argument order in __rfloordiv__.