Key generation support + Swift 4.1 & Xcode 9.3

Fix Xcode 9.1/9.2 warnings

Swift 3.2/4.0 support, errors as enum

Private key header stripping + ObjC layer

Fix Carthage integration

Added Key.reference, Key.originalData, Key.data(), Key.pemString(), K…

…ey.base64String(), Key(reference:)

SwiftyRSA grand refactoring. See CHANGELOG.md for more information

Swift 3.0 + None padding fixes

Swifty RSA 0.4.0

 - Add support for SHA2 (224,256,384 & 512 bits) digest algorithms
 - verifySHA1SignatureData & signSHA1Digest are now deprecated; use verifySignature() and signDigest()
 - Objective-C sign & verification functions now require a digestMethod: parameter
 - Added support to read multiple keys from an input file using publicKeysFromString()
 - Added WatchOS and tvOS support

Added digital signature creation & verification support