Ensuring that '0' paths can be combined into empty URLs
Merge pull request #736 from jamiehannaford/url-combine-0-fix

Ensuring that '0' paths can be combined into empty URLs
Added 'options' to Response->xml() $config parameter.
Simplifying MultipartBody
Does not create a save_to stream until it is used. Closes #715
Renamed 'options' as 'libxml_options'. Updated ResponseInterface->xml() docblock.
Update clients.rst
Merge pull request #738 from jamesfurey/master

Added 'options' to Response->xml() $config parameter.
Added missing default argument

The arguments to the SimpleXMLElement is documented in this way over at PHP.net:
```
data – A well-formed XML string or the path or URL to an XML document if data_is_url is TRUE.
options – Optionally used to specify additional Libxml parameters.
data_is_url – By default, data_is_url is FALSE. Use TRUE to specify that data is a path or URL to an XML document instead of string data.
ns – Namespace prefix or URI.
is_prefix – TRUE if ns is a prefix, FALSE if it's a URI; defaults to FALSE.
```

Even though we never will load XML in directly from a URL in this use case, the thrid argument data_is_url has to explicit be set to false. Otherwise the construct of SimpleXMLElement wont work as expected when the ns and is_prefix is beeing used.
Merge pull request #742 from dkvk/master

Added missing default argument
Merge pull request #740 from jamiehannaford/patch-1

Update clients.rst
Fixing bug in serialzing POST requests
4.1.4 release
Merge branch 'develop'
Merge branch 'master' into develop
Merge tag 'guzzle-v4.1.4' into develop

Conflicts:
	CHANGELOG.md
	composer.json
	docs/clients.rst
	src/ClientInterface.php
	src/main/php/puzzle/adapter/StreamAdapter.php
	src/main/php/puzzle/adapter/curl/CurlFactory.php
	src/main/php/puzzle/message/Response.php
	src/main/php/puzzle/post/MultipartBody.php
	src/main/php/puzzle/post/PostBody.php
	src/test/php/post/PostBodyTest.php
	tests/Adapter/Curl/CurlAdapterTest.php
	tests/UrlTest.php