Silk shouldn't necessarily follow redirects

[matryer]

Silk shouldn't necessarily follow redirects - after all, it's an API testing framework and redirects are part of the API.

Possibly make it false by default, but with an option:

runner.FollowRedirects = true

• see http://stackoverflow.com/questions/23297520/how-can-i-make-the-go-http-client-not-follow-redirects-automatically