call to `strings` in gem/server compatibility should work on paths with spaces

The app I test has a space in the name so the resulting APP_BUNDLE_PATH looks like "/users/sqeaky/wherever/xcode/leaves/app/App Name.app". The space causes strings to see this as two filenames "/users/sqeaky/wherever/xcode/leaves/app/App" and "Name.app". Wrapping that in quotes makes strings interpret this as one argument and allows it to work correctly.

This was tested on Mac OS X 10.8 with XCode 5.1.1 and produced no warnings or error messages.