Add Carthage support

[Palleas]

Hello,

I've added Carthage support for this project I started using. I know it says "Carthage compatible" but it
actually didn't provide a shared Framework scheme. This is the error you'd get if you tried using it:

$  carthage update
*** Fetching SwiftGif
*** Checking out SwiftGif at "v1.5.1"
*** xcodebuild output can be found in /var/folders/tk/cw93k7v928qf21kppt47d_380000gn/T/carthage-xcodebuild.QXYO0e.log
*** Skipped building SwiftGif due to the error:
Dependency "SwiftGif" has no shared framework schemes

If you believe this to be an error, please file an issue with the maintainers at https://github.com/bahlo/SwiftGif/issues/new

Here is what I've done:

• Moved the code from "SwiftGifCommon" into a dedicated "SwiftGif" folder and created the framework scheme
• Renamed the "SwiftGif" target into "SwiftGifDemo"
• I updated the path in the podspec as well and bumped the version number so you can tag / push

Hopefully the travis build should still pass. Let me know what you think about this 😄

[bahlo]

Thank you very much! I will look into this 👍

[Palleas]

The Travis build is failing though, not sure why because I run the same command on my mac and it works 😢

[bahlo]

I think this is the line that is causing Travis to fail. When I run this command on my Mac, the tests still pass, but only after I get the following warning:

[Warning] Tried to install the test host app 'me.arne.SwiftGif' but failed. (3132 ms)
[Info] Preparing test environment failed; will retry 2 more times (0 ms)
[Info] Verified iOS Simulators... (0 ms)
[Info] Shut down iOS Simulator... (0 ms)
[Info] Stopped any existing iOS simulator jobs to get a fresh simulator. (364 ms)
[Info] Reset iOS simulator content and settings at path ...

Travis is failing at the same step: https://travis-ci.org/bahlo/SwiftGif/builds/93796224#L202

[Palleas]

I may have broken something when I moved target around. Didn't notice the warning, thought.
I'll have a look, thanks 😄

[bahlo]

I also saw your tweet and I'm curious and happy to hear what kind of application you use this in (if you can disclose). ☺️

[Palleas]

I'm using it to render Gif in an iOS extension, I'll put it on Github when it's done!

[bahlo]

Merged in v1.6-beta.1 (soon to be master) thank you so much 👍