Better dev tooling in app

- Use Piggieback library for better nREPL+CLJS support
- Include io.pedestal.app-tools.dev namespace instead of a locally
  generated dev.clj
Add io.pedestal.app-tools.build/expand-config for :watch-files
WIP: First attempt at expanding configs from dev tools
Make config.edn -> clj again; Load config when calling (start)

Ran into a problem with edn/read-string and eval. Basically entries like
'project-name.rendering come through edn into ClojureScript as a symbol
with a quote. Attempting to eval the body, however, fails because it
cannot locate the symbols in question

    (eval (edn/read-string "'project-name.rendering"))
    ;; -> CompilerException java.lang.ClassNotFoundException:
    ;;    'project-name.rendering, compiling:(NO_SOURCE_PATH:1:1)

Because of this problem and the annoyance/difficulty of interning
strings as regexps, it seems pertinent to keep the file as Clojure.

Since the config is still executable, but loaded via resources path,
what remains is the question: do we really need the new
expand-app-config functionality, or should we rely solely on functions
called inside that config?
Clean up template

* Remove dev/ and dev/user.clj - it is no longer necessary.
* Add empty config/user.clj - it is unfortunately necessary for
  :repl-options {:init user} to continue to work
* Tidy up app-template's generated project.clj
Switch to EDN config file to showcase non-eval problems

Steps to reproduce

1. lein sub install
2. lein new pedestal-app my-proj
3. In my-proj, launch repl
4. Eval (start)
5. Visit http://localhost:3000/my-proj-dev.html

Inspecting `config` shows what look like the appropriate symbol for
my-proj.start, but ClojureScript is choking on these symbols.
Unquote namespace symbols in config.edn

These quotes are no longer necessary, as reading EDN never evaluates
these symbols.
Don't be quite as eager about reloading config

It didn't make sense to conflate 'start' with 'reload-config' by always
reloading the config. Users may want to manually tweak the config at the
REPL and always reloading would prevent this.
Never fail to launch a REPL in pedestal-app
Merge master -> non-generated-dev-tools
add UI aspect, closes #184
Upgrade to piggieback 0.1.0. Remove REPL-env setup.
Remove old resources dir in app-tools
Documentation updates
First pass at CHANGELOG.md upgrade instructions for 0.2.0
Messing with indentation levels
Clean up CHANGELOG.md for 0.2.0 release
General note in CHANGELOG.md that further action is required...
merge master
Make note in CHANGELOG.md that upgrading tooling to 0.2.0-style is optional.