calabash dylib support - based off PR 463

**FORCE PUSHED** Fri Aug 22 14:55 CET - Based off https://github.com/calabash/calabash-ios/pull/463

**WARNING** Updates the gemspec: run-loop >= 1.0.0.pre4.  1.0.0.pre4 is not released yet. Clients using calabash-ios from master will need to pull run-loop master as well.

### Changes

##### rake build_server 

Updates the rake `build_server` task to run:

* make framework
* make frank
* make dylibs

The default behavior of `rake build_server` is to build the dylibs.  If you don't want to build the dylibs, you can use CALABASH_NO_DYLIBS variable.

```
CALABASH_NO_DYLIBS=1 rake build_server
```

The calabash-ios-server 'make dylibs' task does nothing but print a warning and exit 0.

##### dylib injection API

```
> start_test_server_in_background({:inject_dylib => true})
Calabash::Cucumber::Launcher.new.relaunch({:inject_dylib => true})
```

In the relaunch method, the :inject_dylib value is swapped for a path to a dylib and passed to run_loop.


### Testing

Injecting dylibs is not stable enough for Travis CI.  The simulators are unstable.  I see ~80% passing (in this repo and in the run-loop repo).

To test locally:

```
# all the tests except dylib injection
$ script/ci/travis/local-run-as-travis.rb

# just the dylib injection
$ script/ci/travis/cucumber-dylib-ci.rb
```
### Links

* Adds framework and frank make rules: https://github.com/calabash/calabash-ios-server/pull/55
* Adds dylib targets to calabash server Xcode project: https://github.com/calabash/calabash-ios-server/pull/52  (not yet merged).