Add option to $http for bypassing the processing of request data.

Fixes #121

Changes the behaviour of `$http` such that when `resourceConfigOverrides.skipRequestProcessing` is truthy, every step of the pre-request data processing chain is bypassed. It's not clear from the diff but basically the only change is that all code in `$http` from `promise = this.runInterceptorPhase('beforeRequest'`... to `promise = this.runInterceptorPhase('request'`... is wrapped inside `if (!config.skipRequestProcessing)`.