v1: Remove templating; consolidate to core.clj{s}

Because we now use [om](https://github.com/swannodette/om) and [om-tools](https://github.com/Prismatic/om-tools) for client-side templating, we no longer see the benefit in maintaining the templating portion of dommy for our own use. Simplifying down to just selection, manipulation and events makes it easier for us to keep up with bugs and feature requests as we're still dogfooding those features ourselves.

If anyone is interested in pulling the templating portion out into a separate project and maintaining it, we're happy to help move it over.

## Changes
* Updated ClojureScript, lein-cljsbuild and clojurescript.test dependencies
* Removed all templating-related code (`node`, `deftemplate`, etc.), and removed `dommy.template` ns
* Moved all functions from `dommy.attr` to `dommy.core`
* Renamed `dommy.macros` to `dommy.core`, allowing for:
```clj
(ns foo
  (:require [dommy.core :as dommy :include-macros true]))
```
* Renamed `dommy.core/ancestor-nodes` to `dommy.core/ancestors`
* Added `dommy.core/create-element` and `dommy.core/create-text-node` to make up for removing `node`
* Moved implementation-specific code to `webapp.utils` (for both clj and cljs)
Not crazy about `do-set!`. Function body is already in a `do`, so we can do side-effects first, then put `elem` as last expression. Makes the code easier to understand

```clojure
(defn set-text!
  "Set the textContent of `elem` to `text`, fall back to innerText"
  [elem text]
  (if (.-textContent elem)
    (set! (.-textContent elem) text)
    (set! (.-innerText elem) text))
  elem)
```