Add possibility for reuse to defresource

see https://groups.google.com/forum/#!topic/clojure-liberator/CKl2lPp-3ZY for discussion
when no arguments are provided to defresource, it should generate a function with the request as parameter, instead of a function with 0 arguments that returns a function of request.
Merge branch 'defresource-reuse' of https://github.com/stijnopheide/liberator into stijnopheide-defresource-reuse
Makes resource accept a default config as well

* Shuffles the macro expansion logic at little
* Changes detection of default options to map?
Adds test case for definition default map only
Adds #97 to changes