Making ExternalSpillableMap generic for any datatype

- Introduced concept of converters to be able to serde generic datatype for SpillableMap
	- Fixed/Added configs to Hoodie Configs
	- Changed HoodieMergeHandle to start using SpillableMap

hoodie-common/src/main/java/com/uber/hoodie/exception/HoodieNotSerializableException.java

@@ -0,0 +1,37 @@
+/*
+ *  Copyright (c) 2016 Uber Technologies, Inc. (hoodie-dev-group@uber.com)
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *           http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+package com.uber.hoodie.exception;
+
+import java.io.IOException;
+
+public class HoodieNotSerializableException extends HoodieException {
+
+  private IOException ioException;
+
+  public HoodieNotSerializableException(String msg, IOException t) {
+    super(msg, t);
+    this.ioException = t;
+  }
+
+  public HoodieNotSerializableException(String msg) {
+    super(msg);
+  }
+
+  public IOException getIOException() {
+    return ioException;
+  }
+}