Error thrown when trying to get the number value of a boolean

[JLRishe]

The following throws an error: this.num is not a function:

var num = xpath.parse('"a" = "b"').evaluateNumber();

There is an incorrect method name used in XBoolean.prototype.numberValue(). This will also cause substring() to throw an error if the second or third argument is a boolean value:

var num = xpath.select('substring("hello", 1, "a" = "b")');