Fix "Unable to read data from .......Model.xcdatamodeld/.xccurrentversion"

When using gem:ib and gem:motion_data_wrapper together I get an error like below:
```
rake ib:open
bubble-wrap/camera requires iOS to use.
bubble-wrap/ui requires iOS to use.
rake aborted!
Unable to read data from `#<Pathname:resources/Model.xcdatamodeld/resources/Model.xcdatamodeld/.xccurrentversion>'
/Library/Ruby/Gems/1.8/gems/xcodeproj-0.11.1/lib/xcodeproj/project/object/helpers/file_references_factory.rb:138:in `read_plist'
/Library/Ruby/Gems/1.8/gems/xcodeproj-0.11.1/lib/xcodeproj/project/object/helpers/file_references_factory.rb:138:in `new_xcdatamodeld'
/Library/Ruby/Gems/1.8/gems/xcodeproj-0.11.1/lib/xcodeproj/project/object/helpers/file_references_factory.rb:132:in `each'
/Library/Ruby/Gems/1.8/gems/xcodeproj-0.11.1/lib/xcodeproj/project/object/helpers/file_references_factory.rb:132:in `new_xcdatamodeld'
/Library/Ruby/Gems/1.8/gems/xcodeproj-0.11.1/lib/xcodeproj/project/object/helpers/file_references_factory.rb:27:in `new_reference'
/Library/Ruby/Gems/1.8/gems/xcodeproj-0.11.1/lib/xcodeproj/project/object/group.rb:203:in `new_reference'
/Library/Ruby/Gems/1.8/gems/ib-0.3.5/lib/ib/project.rb:49:in `write'
/Library/Ruby/Gems/1.8/gems/ib-0.3.5/lib/ib/project.rb:48:in `glob'
/Library/Ruby/Gems/1.8/gems/ib-0.3.5/lib/ib/project.rb:48:in `write'
/Library/Ruby/Gems/1.8/gems/ib-0.3.5/lib/ib/tasks.rb:11
Tasks: TOP => ib:open => ib:project
(See full trace by running task with --trace)
```