Example config override for dummy app

[utilityboy]

Possibly closes #3 ?

If you're ok with this approach, I'll update the README as well.

[g-cassie]

@utilityboy The dummy app uses bootstrap right now so I think this will mess up all the formatting. The easiest thing is probably to put this exact example in the README and replace the current section on customizing style (which I think is actually wrong) with a guide.

[utilityboy]

@g-cassie Sorry, I was suggesting to actually leave that code commented out for illustration purposes only. I'll fix.

[g-cassie]

Just want to flesh this out a bit so its crystal clear. Can you change to something like the following.

By default, form master uses the default classes for Bootstrap 3 style forms.  To
change this, extend the `fm-config` service and override the class names that you want.
For a list of the default classes see the base `fm-config` service in:

https://github.com/Emerson/ember-form-master-2000/blob/master/addon/services/fm-config.js

For example for semantic-ui style inputs you would include the following overrides:
formClass: 'ui form',
wrapperClass: 'field',
errorClass: 'error'

[g-cassie]

Just made a comment on fleshing this out so its crystal clear - then I will merge. We can probably just copy and paste roughly the same thing into the README (replacing what is currently there) if you want to add that to the PR as well.