Added jig/ namespace to :components key

1) in README documentation, adding jig/ namespace to :components key, as per this thread: https://groups.google.com/forum/#!topic/clojure/E0BdR_AksiA

2) I didn't touch the :components key in ***src/jig/system.clj***. 

````
$ grep -r ":components" .
./src/jig/system.clj:                      {:components components})))))
./src/jig/system.clj:     :components components
./src/jig/system.clj:    (project-struct (:project-file project) (:components project) false)
./src/jig/system.clj:             (map (juxt :components repeat))
````