0.9.x add git versioning information

companion to server pull request https://github.com/calabash/calabash-ios-server/pull/25

modifies rake task `:build_server` to call server versioning scripts before and after `xcodebuild` call.

```
> server_version
{
   <snip>      
   "git branch" => "0.9.x-add-git-versioning-information",
   "git revision" => "e1abd85",
   <snip>
}
```

#### Motivation

the `server_version` route does not provide enough information about what version of the server is installed on an .ipa.

* when developing features for the server where you might testing and developing several feature branches at once over several days
* when you are presented with a stand-alone ipa and you what to know exactly what features are available in the installed framework