Carthage support

[arturgrigor]

Changes

• Updated the .gitignore file.
• Added the PromiseKit dependency as a submodule.
• Updated the Travis CI config.
• Bumped the podspec version.
• Upgraded the dependency to the latest version.
• Created an Xcode project just for the framework because Carthage needs it.
• Created a single framework target and a single framework tests target for all the supported platforms just like PromiseKit has.
• Updated the Example project and it's Podfile.
• Updated the README.md file to reflect the Carthage support.

[codecov-io]

Codecov Report

Merging #18 into master will decrease coverage by 0.56%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #18      +/-   ##
==========================================
- Coverage     100%   99.43%   -0.57%     
==========================================
  Files           4        7       +3     
  Lines          49      176     +127     
==========================================
+ Hits           49      175     +126     
- Misses          0        1       +1

Impacted Files	Coverage Δ
Tests/AwaitKitAsyncTests.swift	100% <ø> (ø)
Tests/AwaitKitAwaitTests.swift	98.21% <ø> (ø)
Tests/AwaitKitTests.swift	100% <ø> (ø)

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[yannickl]

Oh nice! That's a really great work. Thank you very much!

[arturgrigor]

Thanks! 😀

[arturgrigor]

I forgot to mention that you need to push a new tag, maybe "3.0.2" or "3.1.0" if you want to fully support Carthage.

By default if you specify github "yannickl/AwaitKit" in your Cartfile Carthage will download the latest released version and right now the version 3.0.1 doesn't have Carthage support and that's why a new tag is needed.