erify 0.2.0

Features

• Add check_binary_classes().
• Add where() and related functions for detecting where code is running.
• Add join() and back_quote() to facilitate error message generation.

Changes

• Add n and specific in check_classes() and check_types().
• Replace specifics with specific in validator functions.
• Deprecate n in trigger().
• Deprecate supplement in Statement().

Documentation

• Revise README and vignette.
• Elaborate documentation.