SwiftLint2

Add SourceKit response cache for reducing calls to SourceKit

This depends on https://github.com/jpsim/SourceKitten/pull/135
By applying this, the duration of linting Carthage is reduced from:
```
swiftlint lint  27.85s user 1.98s system 77% cpu 38.538 total
```
to:
```
swiftlint lint  21.15s user 1.26s system 80% cpu 27.743 total
```