update podspec

Merge pull request #114 from serejahh/feature/swift-5-support

Swift 5 support

Merge pull request #104 from Yalantis/feature/swift-4-2

Feature/swift 4 2

Merge pull request #98 from Yalantis/develop

Develop

Merge pull request #87 from Yalantis/develop

Merge with Develop branch

Update README.md