making trim-v before/after symmetrical

[oliyh]

Clone of #280 for develop branch

Hello,

This change will put the untrimmed event vector back in the after phase, making it behave like the original middleware. This is generally a nice thing for interceptors to do, making them additive and not mutating, or at least idempotent.

This then allows other interceptors in the after phase to work better - middleware interceptors generally want to know what the event is called, because they're generic. For example, it lets me write the following improved schema check interceptor:

(defn valid-schema?
"validate the given db, writing any problems to console.error"
[db [event-name]]
(let [res (s/check schema db)]
(if (some? res)
(.error js/console (str "schema problem after event " event-name ":" res)))))
And use it in a stack of interceptors containing trim-v, as long as it's at the end (which it generally will be, because it cleans up the signatures of my event handlers but I don't want it for my middleware interceptors):

(def my-interceptors [(after valid-schema?)
trim-v])

[danielcompton]

Thanks! Merged in ff7c175.