Fixed #232: now we allow interacting with l10n resources from Android's
package:

http://developer.android.com/reference/android/R.string.html

If no package is passed then the application's package is used by default
so we keep backwards compatibility.
Updated documentation to reflect the ability to interact with
Android's String resources as per #232.
Merge branch 'issue-232' of github.com:ustwo/calabash-android into experimental