[TASK] Update php doc for Transformer classes

- Remove wrong @static annotation
- Add missing php doc
[TASK] Add support for ES multi_fields
Merge pull request #12 from ttreeagency/feature/PhpDoc

[TASK] Update php doc for Transformer classes
Merge pull request #11 from ttreeagency/feature/MultiFieldSupport

[TASK] Add support for ES multi_fields

Support only for ES 1.0 or greater