Configuring the core MVC middleware only when calling AddApiVersioning

[denisivan0v]

This change is 

[denisivan0v]

Related to #66

[commonsensesoftware]

I didn't forget about your PR. I'm having trouble with setting up the CLA service (which is required). Boo - rules. Shame on me for not getting that setup months ago.

I'm working on a few other related updates. Since the change appears to only require a single method call change, I'll likely just incorporate this modification manually. I do appreciate the help though. Spasiba!

[denisivan0v]

You're welcome, always glad to help! I'll wait for updates to use them in my apps

[commonsensesoftware]

The code was right, but there were a few other references that needed to be updated. I'm closing this PR since the actual change will occur in PR #92. You can see the exact changes in commit 448f02e.

I also have the CLA requirements properly set up now, which will enable me to easily accept future contributions from the community. Thanks again for your help.