calabash should automatically enable accessibility on the simulator and hide the AXInspector

## motivation

Xcode 5.1 changed the key/value pairs in `com.apple.Accessibility.plist` which broke our strategy for automatically enabling accessibility on the iOS Simulator.

We now check that the accessibility is enabled before we launch.  This can be optimized by caching a variable, but I want some review before I implement this.

- [ ] @krukow - needs review

## testing

I added rspec to the project.

```
$ cd calabash-cucumber
# requires the simulator be available for testing
$ be rake spec
```

- thanks to @rpranata for his pull request 
- thanks to Jari Jegoroff for inspiration

## todo

- [ ] fix command line tool

## other changes

* implemented a logging strategy (tested with rspec)
* implemented some tools for interacting with the Xcode toolchain (tested with rspec)
* implemented tools for interacting with plists (tested with rspec)