Split insert() into insert() & bulkInsert() (#69)

- Behaviour change for existing insert() users
 - Made the current insert() implementation, as something to use for bulkInsert()
 - Normal inserts now share a lot of code with upsert, which provides benefits like small file handling
 - Refactored/Cleaned up code in HoodieWriteClient for reuse
 - Added a unit test, switching few tests to call bulkInsert() and few to call insert()

hoodie-client/src/main/java/com/uber/hoodie/table/HoodieCopyOnWriteTable.java

@@ -25,6 +25,7 @@ import com.uber.hoodie.common.model.HoodieRecordLocation;
 import com.uber.hoodie.common.model.HoodieRecordPayload;
 import com.uber.hoodie.common.model.HoodieTableMetadata;
 import com.uber.hoodie.common.util.FSUtils;
+import com.uber.hoodie.exception.HoodieInsertException;
 import com.uber.hoodie.exception.HoodieUpsertException;
 import com.uber.hoodie.func.LazyInsertIterable;
 import com.uber.hoodie.io.HoodieUpdateHandle;
@@ -376,7 +377,7 @@ public class HoodieCopyOnWriteTable<T extends HoodieRecordPayload> extends Hoodi
 
     @Override
     public Partitioner getInsertPartitioner(WorkloadProfile profile) {
-        return null;
+        return getUpsertPartitioner(profile);
     }
 
     @Override
@@ -385,7 +386,6 @@ public class HoodieCopyOnWriteTable<T extends HoodieRecordPayload> extends Hoodi
     }
 
 
-
     public Iterator<List<WriteStatus>> handleUpdate(String fileLoc, Iterator<HoodieRecord<T>> recordItr) throws Exception {
         // these are updates
         HoodieUpdateHandle upsertHandle =
@@ -449,4 +449,11 @@ public class HoodieCopyOnWriteTable<T extends HoodieRecordPayload> extends Hoodi
             throw new HoodieUpsertException(msg, t);
         }
     }
+
+    @Override
+    public Iterator<List<WriteStatus>> handleInsertPartition(Integer partition,
+                                                             Iterator recordItr,
+                                                             Partitioner partitioner) {
+        return handleUpsertPartition(partition, recordItr, partitioner);
+    }
 }