Simple logging mechanism wrapping timbre

This is a primitive mechanism that wraps timbre's default configuration,
which prints to stdout/stderr.

To add logging to a namespace:

```clojure
(ns my-ns
  (:require [rackspace.logging  :refer [trace
                                        debug
                                        info
                                        warn
                                        error
                                        fatal
                                        report]))
```

Then to log information:

```clojure
(debug "Hey, this thing is useful.")
```

This commit will resolve #6.
Merge pull request #26 from jschairb/timbre_logging

Simple logging mechanism wrapping timbre
Merge branch 'master' of github.com:oubiwann/clj-rackspace into server-payload

Conflicts:
	src/rackspace/api.clj