[PEAK] Use cases for the priority feature

[Alberto Valverde]

  Hi,

Another use-case for the priority feature is when you're extending a 
framework's generic function (eg: jsonify) and you can't (or don't want 
to) modify its source to avoid a conflict with the rule you want to 
register. In this hypothetical case "around" can't be used either since 
the framework (or another library) already defines an around method. The 
only way would be to write a more specific rule but this can be tedious 
and verbose.

Cheers,
Alberto