Pause/resume a consumer by topic (#67)

* Pause a consumer by topic

* Changes per review comments

* convert rvalue to value

* Refactored code to provide a more generic way of getting partition subsets

* Changes per code review and added test cases

* Modified loop to use binary search instead of linear

* Simplify find_matches test cases

include/cppkafka/consumer.h

@@ -193,6 +193,16 @@ public:
      */ 
     void unassign();
     
+    /**
+     * \brief Pauses all consumption
+     */
+    void pause();
+    
+    /**
+     * \brief Resumes all consumption
+     */
+     void resume();
+    
     /**
      * \brief Commits the current partition assignment
      *
@@ -364,7 +374,6 @@ public:
 private:
     static void rebalance_proxy(rd_kafka_t *handle, rd_kafka_resp_err_t error,
                                 rd_kafka_topic_partition_list_t *partitions, void *opaque);
-
     void close();
     void commit(const Message& msg, bool async);
     void commit(const TopicPartitionList* topic_partitions, bool async);