error paths for additionalItems, additionalProperties and patternProperties

This fixes the additionalProperties error path problems issue in #74, which turns out was also affecting patternProperties and additionalItems.

This also fixes a problem with additionalItems, where it was not validating the correct items. See: https://github.com/gazpachoking/jsonschema/commit/4a7ffc107603e5a97462f5871f3c15a2f5430f1b#L0L221