releases, readme: add 2.0.8 release notes (#676)

* releases, readme: add 2.0.8 release notes

* Update format

README.md

@@ -128,6 +128,7 @@
 - [Frequently Asked Questions (FAQ)](FAQ.md)
 - [TiDB Best Practices](https://pingcap.com/blog/2017-07-24-tidbbestpractice/)
 + [Releases](releases/rn.md)
+  - [2.0.8](releases/208.md)
   - [2.1 RC3](releases/21rc3.md)
   - [2.1 RC2](releases/21rc2.md)
   - [2.0.7](releases/207.md)

releases/208.md

@@ -0,0 +1,29 @@
+---
+title: TiDB 2.0.8 Release Notes
+category: Releases
+---
+
+# TiDB 2.0.8 Release Notes
+
+On October 16, 2018, TiDB 2.0.8 is released. Compared with TiDB 2.0.7, this release has great improvement in system compatibility and stability.
+
+## TiDB
+
++ Improvement
+    - Slow down the AUTO-ID increasing speed when the `Update` statement does not modify the corresponding AUTO-INCREMENT column [#7846](https://github.com/pingcap/tidb/pull/7846)
++ Bug fixes
+    - Quickly create a new etcd session to recover the service when the PD leader goes down [#7810](https://github.com/pingcap/tidb/pull/7810)
+    - Fix the issue that the time zone is not considered when the default value of the `DateTime` type is calculated [#7672](https://github.com/pingcap/tidb/pull/7672)
+    - Fix the issue that `duplicate key update` inserts values incorrectly in some conditions [#7685](https://github.com/pingcap/tidb/pull/7685)
+    - Fix the issue that the predicate conditions of `UnionScan` are not pushed down [#7726](https://github.com/pingcap/tidb/pull/7726)
+    - Fix the issue that the time zone is not correctly handled when you add the `TIMESTAMP` index [#7812](https://github.com/pingcap/tidb/pull/7812)
+    - Fix the memory leak issue caused by the statistics module in some conditions [#7864](https://github.com/pingcap/tidb/pull/7864)
+    - Fix the issue that the results of `ANALYZE` cannot be obtained in some abnormal conditions [#7871](https://github.com/pingcap/tidb/pull/7871)
+    - Do not fold the function `SYSDATE`, to ensure the returned results are correct [#7894](https://github.com/pingcap/tidb/pull/7894)
+    - Fix the `substring_index` panic issue in some conditions [#7896](https://github.com/pingcap/tidb/pull/7896)
+    - Fix the issue that `OUTER JOIN` is mistakenly converted to `INNER JOIN` in some conditions [#7899](https://github.com/pingcap/tidb/pull/7899)
+
+## TiKV
+
++ Bug fix
+    - Fix the issue that the memory consumed by Raftstore `EntryCache` keeps increasing when a node goes down [#3529](https://github.com/tikv/tikv/pull/3529)

releases/rn.md

@@ -5,6 +5,7 @@ category: release
 
 # TiDB Release Notes
 
+  - [2.0.8](208.md)
   - [2.1 RC3](21rc3.md)
   - [2.1 RC2](21rc2.md)
   - [2.0.7](207.md)