Merge pull request pusher#36 from pusher/remove-watchOS

Remove watchOS as supported platform

Merge pull request pusher#7 from pusher/release/0.3.0

Update the CHANGELOG file for v0.3.0 release

Merge pull request pusher#5 from pusher/release/0.2.1

Update the CHANGELOG file for v0.2.1 release

Merge pull request pusher#2 from pusher/feature/carthage-support

Carthage support

Merge pull request pusher#1 from pusher/tech/swift-tools-version-5.0

Updates for 'Package.swift'