Ensure compatible arch before launching on device

### Motivation

**Before launching an app on iOS, ensure that the architecture of the CFBundleExecutable is compatible with the target device.** [#75](https://github.com/calabash/run_loop/issues/75)

If the binary and the _simulator_ target are not compatible, an error will raised _before_ launch.

```
RunLoop::IncompatibleArchitecture: Binary at:
/Users/moody/git/run-loop/spec/resources/lipo/x86_64/chou.app/chou
does not contain a compatible architecture for target device.
Expected 'i386' but found ["x86_64"].
```

### Todo

- [x] ~~I think we need some error handling in the RunLoop::Lipo class.~~  UPDATE:  Let's forgo the error handling until becomes an issue.

### Missing behaviors

There are two compatibility checks that are missing:  is the binary compatible with a _physical device_ and is the binary compatible with the _form factor_.

Checks against physical devices will require integrating a tool like `ideviceinfo` because we cannot find information about a device's instruction set using Xcode tools; all we have is the UDID.

We _can_ check that the binary is compatibility with the form factor (e.g. Is this an iPad only app?) by inspecting the Info.plist.  This behavior belongs in another PR.

### Testing

```
$ be rake spec/integration/simulator_compatibility_spec.rb
Simulator/Binary Compatibility Check
  raises an error if libraries are not compatible
    targeting i386 simulator with binary that contains only a x86_64 slice
    target only has arm slices
  can launch if library is FAT
    targeting x86_64 simulator with binary that contains only a i386 slice
    can launch if libraries are compatible
```

@krukow @svevang