Add Boolean data type.
It's not clear to me why there isn't a Boolean class which can have values true and false.
There are benefits to this. An example of where this is an issue is people who write ORM. For example, in
sequel gem, they use "TrueClass" for a boolean column.
The naming of TrueClass and FalseClass are also inconsistent with other names, e.g. it's not IntegerClass or FloatClass or StringClass.