ReactiveCocoa.xcodeproj doesn't specify iOS target version

[carlbrown]

When trying to compile RACiOSDemo/RACiOSDemo.xcodeproj on a version of Xcode that doesn't target iOS 5.1 as the default (REDACTED, for example), the target iOS target for the demo is set to iOS 5.1, and it builds correctly, but the Framework is only built for the default version, so when the Demo runs, the Framework won't load because it has the wrong target.

This leads to immediate crash with runtime error:

dyld: lazy symbol binding failed: Symbol not found: _objc_setProperty_nonatomic_copy

And I figured I'd save someone else the trouble of figuring out what the Hell Xcode meant by that.

[carlbrown]

Pull request FAIL. Sorry - was trying to attach the pull request to this issue, but ended up making a new one.