Fixed relationships not being namespaced when needed

Before creating a relationship it does a check to see if the main class is namespaced, and if so, appends the namespace to relationship, otherwise it leaves it as is.

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Really sorry as I have no idea how to attach a pull request to an existing issue. The issue is described as here: https://github.com/JeffreyWay/Laravel-Test-Helpers/issues/7

This fixes it from what I can tell (my tests now work as they failed before) and your tests all run green still.

Hope that helps :-)