Swift contribution layer

[ghost]

Basic support for Swift (scripting).

Only customization for Spacemacs available is basic support for switching back and forth from the REPL.

[robbyoconnor]

Next time do a search -- duplicate of #2536

[TheBB]

This one seems more complete though.

CC @myrjola

[robbyoconnor]

Still -- it seems like duplicate work is better done collaboratively on the same PR -- similar to what happened with #2845

[ghost]

Hmm... pretty sure I did... anyhow, this one adds the edit-to-repl roundtrip and enables flychecking. How should we proceed?

[robbyoconnor]

@usharf -- Personally (my opinion doesn't carry any weight other than I care) -- I'd leave it. If it literally just duplicated #2536 -- but you added more than that PR had so -- as I said leave it :)

[myrjola]

@usharf Good work! I closed my pull request as it does bring fever things to the table than yours. Let's hope yours gets merged.

[ghost]

👍 @myrjola

[d12frosted]

It has some problems.

1. You need to set flycheck-swift-sdk-path to something like "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk". Otherwise you'll see File mode specification error: (void-variable flycheck-swift-sdk-path) on visiting swift file. So it should be part of installation guide.
2. After that when you visit swift file you'll see another problem - eval-after-load: Symbol's value as variable is void: swift. How to fix that I am not sure :-P

[d12frosted]

Plus, swift-mode doesn't support swift 2.0, so it's kinda pointless at this point.

[syl20bnr]

At @TheBB request I merged it, if there are some issues with it, don't hesitate to mention them in the README.
Thank you !
Cherry-picked into develop branch, you can safely delete your branch.