Remove Rx from Needle examples

[ebgraham]

The Needle sample projects are overly complicated and have no particular need for a dependency on Rx and Carthage. Examples should ideally have no dependencies outside of vanilla iOS and Needle, and allow the developer to focus use of the framework. Rx makes following the project calls complicated and raises the bar for learning from the examples.

[neakor]

This is a great point! The current sample is simply a port of Uber's internal training material. Internally we use Rx heavily, hence why that got ported over as well. We should definitely update this. Do you think you can help with this @ebgraham ?

[monishsyed]

Hey @neakor @ebgraham, Hope you all are doing well. I took a stab adding a non-rx sample to the repo :) Would be great to have your eyes on it. Looking forward to the feedback. Thank you :)

#356