Fix fatal error in RequestMediator::writeResponseBody() when malformed response is recieved

https://github.com/guzzle/guzzle/issues/408
Visit children who have xmlAttribue first when building up xml
Minor tweak
Merge remote-tracking branch 'natmchugh/check-childen-have-attribues'
Tweak
Only exploding on header glue when not inside of a comma. Closes #411
Making mimetype guessing case-insensitive
Only injecting schema in models when specified in OperationResponseParser constructor. Models still always return a Parameter object when calling getStructure(), but this cleans up var_dump and var_export for most use cases. Closes #402
Adding a new line after debug model output
Changed test to show JsonVisitorTest::testAddsJsonHeader fail
Changed test to show XMLVisitorTest::testSerializesXml fail
Fix JSON and XML request visitors to set Content-type before body
Removed guessing of request body content type by request path. Reverts part of 863998bb.
Merge pull request #414 from checat/adds-json-header-fail

Json and XML visitors do not set correct Content-type when path has known extension
Fixed typo in request options description for auth
Merge pull request #416 from konradpodgorski/patch-1

Fixed typo in request options description for auth
ChunkedIterator for Traversable - Regression Test
ChunkedIterator for Traversable - Fixed
ChunkedIterator valid is a bool of chunk

Just some minor code cleanup. The negation of empty is just not necessary and rather clumsy.
ChunkedIterator tests for boundary cases and and below zero.