Revamped Deltastreamer (#93)

* Add analytics to site

* Fix ugly favicon

* New & Improved HoodieDeltaStreamer

 - Can incrementally consume from HDFS or Kafka, with exactly-once semantics!
 - Supports Json/Avro data, Source can also do custom things
 - Source is totally pluggable, via reflection
 - Key generation is pluggable, currently added SimpleKeyGenerator
 - Schema provider is pluggable, currently Filebased schemas
 - Configurable field to break ties during preCombine
 - Finally, can also plugin the HoodieRecordPayload, to get other merge types than overwriting
 - Handles efficient avro serialization in Spark

 Pending :
 - Rewriting of HiveIncrPullSource
 - Hive sync via hoodie-hive
 - Cleanup & tests

* Minor fixes from master rebase

* Implementation of HiveIncrPullSource
 - Copies commit by commit from source to target

* Adding TimestampBasedKeyGenerator
 - Supports unix time & date strings

hoodie-client/src/main/java/com/uber/hoodie/HoodieWriteClient.java

@@ -64,6 +64,8 @@ import java.nio.charset.StandardCharsets;
 import java.text.ParseException;
 import java.util.Collections;
 import java.util.Date;
+
+import java.util.HashMap;
 import java.util.List;
 import java.util.Optional;
 import java.util.stream.Collectors;
@@ -317,6 +319,16 @@ public class HoodieWriteClient<T extends HoodieRecordPayload> implements Seriali
      * Commit changes performed at the given commitTime marker
      */
     public boolean commit(String commitTime, JavaRDD<WriteStatus> writeStatuses) {
+        return commit(commitTime, writeStatuses, Optional.empty());
+    }
+
+    /**
+     * Commit changes performed at the given commitTime marker
+     */
+    public boolean commit(String commitTime,
+                          JavaRDD<WriteStatus> writeStatuses,
+                          Optional<HashMap<String, String>> extraMetadata) {
+
         logger.info("Comitting " + commitTime);
         // Create a Hoodie table which encapsulated the commits and files visible
         HoodieTable<T> table = HoodieTable
@@ -333,6 +345,10 @@ public class HoodieWriteClient<T extends HoodieRecordPayload> implements Seriali
         for (Tuple2<String, HoodieWriteStat> stat : stats) {
             metadata.addWriteStat(stat._1(), stat._2());
         }
+        // add in extra metadata
+        if (extraMetadata.isPresent()) {
+            extraMetadata.get().forEach((k, v) -> metadata.addMetadata(k, v));
+        }
 
         try {
             String actionType = table.getCommitActionType();