Updated Carthage info in README
Updated Carthage info in README

VirgilSecurity/virgil-sdk-keys-x,VirgilSecurity/virgil-sdk-keys-x,VirgilSecurity/virgil-sdk-keys-ios,VirgilSecurity/virgil-sdk-keys-x,VirgilSecurity/virgil-sdk-keys-ios,VirgilSecurity/virgil-sdk-keys-ios,VirgilSecurity/virgil-sdk-keys-x,VirgilSecurity/virgil-sdk-keys-ios