Ios8 fast performtask

Implements a faster version of the "host" strategy for communicating with UIAutomation. The idea is to use a pipe and have the UIAutomation script do a blocking read on the pipe (see `scripts/read-cmd.sh`) instead of a loop that polls frequently. The idea is similar to the technique called "long polling" used in ajax-based web-apps. Overall the responsiveness is better than the fast-poll approach.

This pull request also features ability to specify options

- `:uia_strategy` (should be :host or :preferences) for picking strategy for talking with UIAutomation

- `:calabash_lite` (should be true/false) implies `:host` strategy and stores this in the `run_loop` hash