Prevent TripIt::Profile#trips from blind caching
Prevent TripIt::Profile#trips from blind caching

* Since you can pass different params to #trips, it shouldn't just
  cache the result since the results can be different with
  different parameters.
  - eg. user_profile.trips and user_profile.trips(:past => true) will
        return different results and need to be cached differently

flyertools/tripit,flextrip/tripit