previously, we used multiple different projects for various targets (app, test, render) that overwrote each other, so it was impossible to have one project to build them all, one project to compile them, one project to run them all and in the darkness bind them
This podspec was originally lifted from mapbox/mapbox-ios-sdk, which was structured and built quite differently. We could have the podspec build this repo as is, using scripts/package_ios.sh, but that would require developers to install the same version of Xcode as Travis is using (see #977). So this podspec instead pulls a prebuilt library. Much simpler.
Also package a LICENSE with the archive to satisfy a CocoaPods warning.
Fixes#829.
xcodebuild does not require a specific SDK version, but Mason puts packages in a version-specific directory. So this change uses the logic for $MASON_PLATFORM_VERSION in mason.sh in mapbox/mason.
Fixes#974.
