Update Podspec

Release 2.2.1

Merge pull request mattdonnelly#235 from mattdonnelly/swifter-2.2

Swifter 2.2

Podspec update

Update version for Pods

Add support for Swift Package Manager

Merge pull request mattdonnelly#159 from mattdonnelly/swift-3

Swifter 2.0 with Swift 3

Merge pull request mattdonnelly#135 from lewis-smith/master

Moved to stringByAddingPercentEncodingWithAllowedCharacters

Merge pull request by meteochu and remove test target

Merge pull request mattdonnelly#92 from s-aska/fix_bug_bool_cast_anyo…

…bject

Bool being seen as int when using AnyObject