carthage 0.4 (new formula)

A work-in-progress for Carthage 0.4 when it is released. Using my fork until my Makefile changes (or something similar) end up upstream.

Currently the test is failing. It shouldn't be so I'll need to look at that.

Follows on from #34677. CC @robrix @Keithbsmiley.
Aaah:
```
Check dependencies
Code Sign error: No code signing identities found: No valid signing identities (i.e. certificate and private key pair) matching the team ID “(null)” were found.
CodeSign error: code signing is required for product type 'Framework' in SDK 'iOS 8.1'
```

On it.