rename index to app

follows general nodejs convention
helper shouldn't require itself
listen takes callback when server is ready
use nconf for config
updated dependencies
separate image-specific features from http req/res

- use image_request class to deal with images (taking some of that responsibility from the helpers)
- the app now receives requests, attempts to deliver from static fs, and directs the image_request to perform resizing etc.
set user-agent on requests
pathname does not include query
add component logging
correct and clarify resize command
mkdirp directory when starting resize
image request now responsible for writing cached file

- app now calls resize directly
cleanup
don't use file cache if set to false
start of test framework
revert index->app rename
Merge branch 'master' into refactor

Conflicts:
	lib/helpers.js