Align RoboSputnik::getConfig with RobolecticTestRunner

[pelotasplus]

We use heavily modified getConfig method and it seems that one provided by Robolectric has some features we don't support.
Most probably we can just use the original method from Robolectric 3.0

[pjakubczyk]

I'd rather make a note on the webpage that RoboSpock doesn't allow to annotate methods with @config because of its internals ...

[farrukhnajmi]

Any example on how to make robospock 1.0.1 with robolectric 3.4.2 to provide custom config. See problem I had with bottom of this post:

https://stackoverflow.com/q/46314008/256770