Fix iOSFrameworkSpecs for Xcode 5.1

- Create fat binary in Debug mode too
- Remove explicit ARCHS setting from command line build
- Requires iOS 7.0 simulator to run from command line (same for rake install)
Further tweaks to iOSFrameworkSpecs target attempting compatibility with Xcode 5.1 and 5.0 (mainly for travis.ci)

Adds missing armv7s to fat binary static framework and restores ARCHS in rake iosframeworkspecs
Raise error during rake tasks that require
iOS simulator that is not installed
Merge pull request #205 from pivotal/fix_iOSFrameworkSpecs

Fix iOSFrameworkSpecs for Xcode 5.1