[Ruby] Release 0.50.1

Changed

• CanonicalSchema#satisfiability answers :yes for a string whose pattern or format a matching value can be built from.
• CanonicalSchema#satisfiability answers :no where a format takes no string of the length the schema asks for.

Fixed

• CanonicalSchema#negate taking apart a union that reads a definition through its own if, so a schema and its negation shared a value.
• CanonicalSchema#subtract dropping a Draft 4 array member an element demand partly takes.
• CanonicalSchema#covers answering Yes where a Draft 4 element demand refuses a member.
• A string schema whose maxLength is 0 keeping a pattern, format, or content facet unread, so the same constraints written in one object and written as an allOf reached different canonical forms.

Performance

• not over a wide object schema costs its branch count instead of its square.
• not over an object schema is linear in its property count, not quadratic.
• not over an object schema with additionalProperties: false no longer costs cubic time in its property count.