Fixed: Return correct VCR call in error message.
Fixed: Comparison of header values can contain regex chars (like +).

What is actually needed is a equal comparison instead of a match with regex.
Fixed: Uses headers as given, instead of lowercase them.

Guzzle lowercases the header names in their array but
actually they should be stored in their original form.
Implemented: CURLOPT_HEADER is recognized when handling output.
Fixed: curl_getinfo() returns info array with correct keys.
Implemented: Removes Content-Type header when setting a empty CURLOPT_POSTFIELDS array.
Fixed: Removes old guzzle unittest fixture.
Fixed: Prevents guzzle from setting the User-Agent to allow request matching on different systems.
Merge pull request #56 from php-vcr/httpful-fixes

Httpful fixes