get (req|res) message and entity len

From libHTP in htpy.h struct htp_tx_t:
* htp_tx_t->request_message_length
* htp_tx_t->response_message_length
* htp_tx_t->request_entity_length
* htp_tx_t->response_entity_length
Update README
Whitespace and style cleanup.
Merge branch 'pr/9'