v0.4.0

• Added AWSLoggingMiddleware which logs raw requests sent to AWS and raw responses received back.
• Changed restjson protocol Content-Type header to be 'application/json'.
• Created AWSResponse struct which holds a processed response.
• Middleware now has the ability to edit the contents of a AWSResponse.
• Separated service signing name from service endpoint name as these can sometimes be different.
• If response has a payload path then create top level objects to contain the response json or xml.
• Mac uses CommonCrypto for SHA256, HMAC and MD5 calculations.
• Added AWSClient.signURL() to return a signed URL.
• AWSErrorType now conforms to CustomStringConvertible.
• Add additional methods for decoding timestamps (HTTP date format and seconds from UNIX epoch time).
• AWSClient.send() functions don't throw errors so have removed throws from them.
• Min/max collection length validation errors output the length and not the full collection.
• String pattern validation does not expect the whole string to match the pattern.