[Docs] Tidy up README a bit.
[Docs] Tidy up README a bit.

apple/swift-package-manager,vmanot/swift-package-manager,sschiau/swift-package-manager,vmanot/swift-package-manager,haskellswift/swift-package-manager,vmanot/swift-package-manager,sschiau/swift-package-manager,apple/swift-package-manager,apple/swift-package-manager,mxcl/swift-package-manager,sschiau/swift-package-manager,abertelrud/swift-package-manager,mxcl/swift-package-manager,abertelrud/swift-package-manager,vmanot/swift-package-manager,abertelrud/swift-package-manager,haskellswift/swift-package-manager,JGiola/swift-package-manager,abertelrud/swift-package-manager,JGiola/swift-package-manager,apple/swift-package-manager,JGiola/swift-package-manager,abertelrud/swift-package-manager,sschiau/swift-package-manager,haskellswift/swift-package-manager,sschiau/swift-package-manager,haskellswift/swift-package-manager,JGiola/swift-package-manager,vmanot/swift-package-manager,mxcl/swift-package-manager,mxcl/swift-package-manager,JGiola/swift-package-manager,apple/swift-package-manager