Merge in changes from upstream for socialengineers multipart fork

v1.5:

- Added support for running multiple queries under the same Query object
- Added support for running multiple queries under the same QueryBuilder object
- Updated tests to cover new functionalities added
- Added examples in the README.md file

- Add ability to set third parameter in constructor to override Guzzl…

…e httpOptions

- Modified tests to be Windows-friendly

Issue 13: Fixed issue in setting null argument values

Added support for inline fragments in Query and QueryBuilder

v1.2: Add support for variables

GQL-46