Added Carthage/Build to .gitignore
Added Carthage/Build to .gitignore

When using the option `--use-submodules` with Carthage, the `Carthage/Build` directory shows in the submodule after `carthage build` making the submodule dirty.
boredzo/iso-8601-date-formatter,boredzo/iso-8601-date-formatter,boredzo/iso-8601-date-formatter