Add kafka library and integrate it into memgraph

Summary:
Integrated kafka library into memgraph. This version supports all opencypher
features and will only output messages consumed from kafka.

Depends on D1434

Next steps are persisting stream metadata and transforming messages in order to
store them in the graph.

Reviewers: teon.banek, mtomic, mferencevic, buda

Reviewed By: teon.banek

Subscribers: mferencevic, pullbot, buda

Differential Revision: https://phabricator.memgraph.io/D1466

libs/setup.sh

@@ -127,3 +127,8 @@ tar -xzf capnproto.tar.gz
 rm -rf capnproto
 mv capnproto-c++-0.6.1 capnproto
 rm capnproto.tar.gz
+
+# kafka
+kafka_tag="c319b4e987d0bc4fe4f01cf91419d90b62061655" # Mar 8, 2018
+# git clone https://github.com/edenhill/librdkafka.git
+clone git://deps.memgraph.io/librdkafka.git librdkafka $kafka_tag