Support Carthage

[taterbase]

Many iOS projects these days are making use of Carthage for dependencies instead of CocoaPods. Currently the MojioSDK requires you to use CocoaPods to install its dependencies which breaks the ability to use MojioSDK as a Carthage dependency.

There are two ways to solve this.

1. Bundle MojioSDK's dependencies in the git repo and increase the size of the project overall.
2. Convert MojioSDK to use Carthage for dynamic dependency building

Both options still allow MojioSDK to function and install as a CocoaPod. The only change is how you develop on MojioSDK.

Option 2 replaces pod install inside the mojio-ios-sdk project you with carthage update. You would not need to use the .xcworkspace anymore.

Option 1 has no build step as the frameworks are already bundled.

I'll be pushing a PR for the swift4 branch that makes the changes necessary for option 2. I think this is a big benefit for the MojioSDK and does not impact development on the sdk severely. Please leave any feedback on how I can improve this as I'd like to see it merged in.