Add option to enable real HTTP requests

[luisobo]

At this point, when Nocilla is enabled, any HTTP request will be handled by Nocilla and won't hit the outside world. This is the desired behavior for unit tests but disabling this behavior may be convenient for other scenarios.

[robertomg]

+1

[raphaeloliveira]

+1

[pbernery]

+1
One of the scenarios would be using Nocilla directly in the app and stub Web Services not developed yet.

[prudencioj]

This would be very helpful! +1

[marhas]

+1

[sghiassy]

+1

Had to switch to https://github.com/AliSoftware/OHHTTPStubs for this feature