PHP client implementation

- implemented a working client in PHP
	- reimplemented the ruby implementation
	- tests querying w/ and w/o transactions
- updated the readme with installation instructions for PHP dependencies

__known limitations__:
- socket needs reinstantiation before every send op
    - reason seems to be the short answer from the server (i.e. 1byte representing an empty object in MessagePack)
    - causes the socket to stay in receive mode, even though it returns the received data as expected