Fixed issue where KeywordArgs is not checked if it is a hash.
Fixed issue where KeywordArgs is not checked if it is a hash.

This leads to issues when methods are overloaded, because when the
KeywordArgs gets checked on a non-hash argument, it raises an exception
rather than failing properly.

smt116/contracts.ruby,egonSchiele/contracts.ruby,smt116/contracts.ruby,egonSchiele/contracts.ruby