As a fallback that allows for other gems defining them, only define
Boolean and XmlContent if they're not already defined.
Currently unhappymapper and the boolean gem are incompatible, because unhappymapper defines Boolean as a class, and the boolean gem defines it as a module.
This patch will load the boolean gem if available and fall back to defining Boolean locally, but only if Boolean is not already defined (I did the same for XmlContent just in case too), so if there are other gems that define these consts as something other than class, you can load them before unhappymapper and things will be happy.
As a fallback that allows for other gems defining them, only define Boolean and XmlContent if they're not already defined.
Currently unhappymapper and the boolean gem are incompatible, because unhappymapper defines Boolean as a class, and the boolean gem defines it as a module.
This patch will load the boolean gem if available and fall back to defining Boolean locally, but only if Boolean is not already defined (I did the same for XmlContent just in case too), so if there are other gems that define these consts as something other than class, you can load them before unhappymapper and things will be happy.