Reorganized services so you can load and write the same file

The previous services were nicely decoupled however because they were
writers were created with blank excel objects, not the object in the
main service being utilized. This way provides a service that can load
files modify them and then output them in multiple formats

This fixes both open issues you currently have #43 and #36

The real issue was that your original services uses the factory method and passes it the 'service' of a blank php excel object.