* reimplemented basic requests with httpplug
* added returning headers
* added query params support
* removed constant reference to model class
* some extra @throws; form params
* form and query params encoding
* file upload / form multipart
* added missing response headers in WithHttpInfo calls
* removed Store test From PetApiTest class
* removed configuration overriding test as its now task of client adapters
* updated store tests with new client initialization code
* updated composer.json template
* not using json_decode if response is string
* renamed some variables to camelCase
* removed ApiClient and Configuration classes
* added HeaderSelector template
* added ObjectSerializer injection
* regenerated all samples
* added AuthConfig and readded support for custom api keys
* readded support for oauth tokens
* readded basic auth; moved auth tests to separate test class
* readded header params
* readded support for collections in paths
* readded config option; readded exception handling
* file downloading; readded some Configuration properties removed earlier
* readded default headers
* made responses and return types work same way as earlier
* made all methods static in ObjectSerializer
* updated test.php, replaced autoload.php with composer's autoloader
* updated api doc template
* removed classes used for testing; regenerated Fake_classname_tags123Api
* replaced httplug with guzzle6
* updated required php version to 5.5
* clean up
* readded missing userAgent feature; removed default headers from Configuration
* updated test.php
* downgraded phpunit back to 4.8 to work with php5.5; fixed client initialization in some tests
