Add python table api section to the roadmap.

This closes #204

roadmap.md

@@ -154,6 +154,13 @@ the catalogs ([FLINK-10232](https://issues.apache.org/jira/browse/FLINK-10232)).
 There is a broad effort to integrate Flink with the Hive Ecosystem, including
 metastore and Hive UDF support [FLINK-10556](https://issues.apache.org/jira/browse/FLINK-10556).
 
+There is also a big effort to support Python for Table API [FLIP-38](https://cwiki.apache.org/confluence/display/FLINK/FLIP-38%3A+Python+Table+API).
+We will divide the work into following stages:
+
+- Translate Python Table API queries without UDFs to Java and run them completely in Java for the first step.
+- Add support for User-defined functions(Scalar Function/Table Function/Aggregate Function) in the second step.
+- Integrating Pandas as the final effort, i.e., functions in Pandas can be used in Python Table API directly.
+
 # Connectors & Formats
 
 Support for additional connectors and formats is a continuous process.

roadmap.zh.md

@@ -100,6 +100,13 @@ Flink Web UI 正在移植到更新的框架中并获得其他功能并更好地
 
 还有一个巨大的工作是将 Flink 与 Hive 生态系统集成。包括 Metastore 和 Hive UDF 支持 [FLINK-10556](https://issues.apache.org/jira/browse/FLINK-10556)。
 
+社区在Table API支持Python方面也做出了很多的努力 [FLIP-38](https://cwiki.apache.org/confluence/display/FLINK/FLIP-38%3A+Python+Table+API)。
+我们将工作分为以下几个阶段:
+
+- 首先以将Python Table API 直译为Java Table API的方式支持用户编写没有UDFs(标量函数/表值函数/聚合函数)的Python Table API程序。
+- 增加对UDFs(标量函数/表值函数/聚合函数)在Python Table API的支持。
+- 最后将Pandas与Python Table API进行集成，Pandas中的函数可以在Python Table API中直接使用。
+
 # Connectors & Formats
 
 支持额外的 connectors 和 formats 是一个持续的过程。