Improve Tutorial and Setup Instructions

[billburgess]

I was able to get things working just from the ease of using Cocoapods, but many users won't be as lucky. Also, the tutorial is very, very limited. It would be nice to have instructions for how to get this to work when used only within XCTest classes (which is kind of the point of the project). The example project does not include any tests written against the sample project. These tests would be great examples of how to use VCRURLConnection from a unit-test standpoint. I've been unable to find any outside tutorials online on how to use this successfully with Tests. I'm relatively new to testing, so I don't fully understand how everything works together and I'm sure many more users could benefit from this tool and better setup/tutorials. Thanks!