Fixed & documented Composer integration & Redis arg fatals

I had problems getting going with this library because of a couple of unmerged PR's, this fork represents everything I had to merge to get going, as well as updates to the README.md describing how the library is now to be used (assuming you're using Composer).

- Includes #10 & #12, which in turn resolves #8.
- Adds bin definition into `composer.json` so the worker is installed in the same place as `php-resque`, `vendor/bin`.
- Also updates README.md code & worker examples.

@chrisboulton :eyes: