concern(name, callable = nil, &block)
Instance Public methods
Define a routing concern using a name.
Concerns may be defined inline, using a block,
or handled by another object, by passing that object as the second
parameter.
The concern object, if supplied, should respond to call, which
will receive two parameters:
* The current mapper
* A hash of options which the concern object may use
Options may also be used by concerns defined in a block by accepting a
block parameter. So