0.2.0

New features:

• Generalised binary_op and fused_binary_flip_op for implementing advanced custom Bdd operations.
• Added var_project/var_select/var_pick and project/select/pick for working with Bdd as relations (#6).
• Display for Bdd uses default text format.
• BddSatisfyingValuations iterator over all BddValuations that satisfy given Bdd.
• Better API for working with BddValuations (#1 and #7).
• Some small utility methods, like BddVariableSet.mk_literal.

Breaking changes:

• Some &Vec<T> arguments were changed to &[T] as suggested by clippy.

Other changes:

• Stricter CI scripts and git hooks.
• Fix all clippy warnings and errors.