1. Adopting a marker interface for Guzzle exceptions.
A. All exceptions emitted from Guzzle are now wrapped with a Guzzle namespaced exception.
B. Guzzle\Common\GuzzleExceptionInterface was renamed to Guzzle\Common\GuzzleException
C. Guzzle\Common\ExceptionCollection was renamed to Guzzle\Common\Exception\ExceptionCollection
2. Using Header objects for Request and Response objects
A. When you call $request->getHeader('X'), you will get back a Guzzle\Http\Message\Header object that contains all of the headers that case insensitively match. This object can be cast to a string or iterated like an array. You can pass true in the second argument to retrieve the header as a string.
B. Removing the old Guzzle\Common\Collection based searching arguments from most of the request and response header methods. All retrievals are case-insensitive and return Header objects.
3. Changing the two headers added by the cache plugin to just one header with key and ttl.
4. Changing Guzzle\Http\Message\Response::factory() to fromMessage().
5. Removing the NullObject return value from ServiceDescriptions and instead simply returning null
New Features / enhancements:
1. Adding Guzzle\Http\Message\AbstractMessage::addHeaders()
2. Making it simpler to create service descriptions using a unified factory method that delegates to other factories.
3. Better handling of ports and hosts in Guzzle\Http\Url
Note: This is a noisy diff because I'm removing trailing whitespace and adding a new line at the end of each source file.
