Minor version

Minor version introducing new features with no breaking changes:

• Add an error string checker, e.g. check(new TypeError(), "error")
• When ValueError auto-prefixes the name of the calling function, it skips anonymous functions in the stack
• When ValueError auto-prefixes the name of the calling function, it doesn't if the prefix already includes a ': ' colon space.
• Add return string type modifier, e.g. check(123, return num) (changes error message to e.g. Must return X)