GWT Contacts - Bugfixing

I created this pull request to fix a bug and to answer Issue #30.

The bug: when we click cancel or save that app does not redirect to the list, and on cancel we also get a null pointer exception.

The changes include:

* external stylesheet for contacts view instead of inline styles
* rename the ready event in edit-contact-view (Dart Editor showed a warning that ready exists in the parent class)
* set _originalContact in enteredView (in the constructor it is still null, but if we don't set it, we get an exception in cancel, that's why the app doesn't redirect to the list)

This way I don't find any bugs, the redirection works fine.