Update LSNSURLSessionHook.m

In the current implementation, the presence of [NSURLSessionConfiguration class] in the ternary appeared to cause the class to be loaded - even though it isn't returned - and that was causing side effects in iOS7.  Replacing that with NSClassFromString worked.  I also split that long line up.
Fixed failing Travis build

Fix for the failing travis build.

I got the fix from here: http://docs.travis-ci.com/user/osx-ci-environment/
Merge pull request #76 from augustj/iOS8-Fix

Update LSNSURLSessionHook.m
Merge pull request #78 from ajimix/patch-1

Fixed failing Travis build