has_key? returns nil when key not found

[boricic]

Playing around with the gem I've noticed that has_key? method returns nil if the key is not found.

Shouldn't, by generally accepted convention, a method ending with ? return always Boolean?

I can see that method for has_key? might be wrong. The comment says that it returns true/false, but actually it returns Qnil.

https://github.com/tyler/trie/blob/master/ext/trie/trie.c#L87