update release notes [skip ci] (#939)

* update release notes [skip ci]

Author: mr-salty

google/cloud/spanner/README.md

@@ -16,4 +16,58 @@ production workloads.
 
 ## Release Notes
 
-### v0.1.x - TBD
+### v0.3.x - TBD
+
+### v0.2.x - 2019-10
+* **Breaking Changes**
+  * refactor `Read` to return `ReadResult`; remove `ResultSet` (#935)
+  * removed `Row<>` from mutations API (#938). Removes the `AddRow(Row<Ts...>)`
+    member function on the `WriteMutation` API. In place of this method there
+    is now an `AddRow(std::vector<Value>)` method.
+  * Change `Value::Bytes` to `google::cloud::spanner::Bytes` (#920)
+  * implement `CreateInstanceRequestBuilder` (#933). Changed the function
+    signature of `InstanceAdminClient::CreateInstance()`.
+  * Replace `ExecuteSql` with `ExecuteQuery` and `ExecuteDml` (#927)
+  * Changed `RowParser` to require a `Row<Ts...>` template param (#653).
+    `ResultSet::Rows` used to be a variadic template that took the individual
+     C++ types for each row. With this change that function is now a template
+     with one parameter, which must be a `Row<...>` type.
+  * Implements `Database` in terms of `Instance` (#652). This PR removes
+    renames some accessors like `InstanceId` -> `instance_id` due to their
+    trivial nature now (style guide). It also removes some methods like
+    `Database::ParentName()`, which is now replaced by `Database::instance()`.
+  * Fixes inconsistent naming of the Batch DML params struct. (#650). This
+    struct has been renamed, so any code using this struct will need to be
+    updated.
+
+* **Feature changes**
+  * implement `InstanceAdminClient` methods `CreateInstance`, `UpdateInstance`,
+    `DeleteInstance`, `ListInstanceConfigs`, `GetInstanceConfig`,
+     `SetIamPolicy`.
+  * implement `DatabaseAdminClient` methods `TestIamPermissions`,
+    `SetIamPolicy`, `GetIamPolicy`.
+  * implement retries for `Commit()`, `PartitionRead`, `PartitionQuery`,
+    `ExecuteBatchDml`, `CreateSession`, `Rollback`.
+  * implement `PartialResultSetRead` with resumes (#693)
+  * use separate policies for retry vs. rerun (#667)
+  * implement `DatabaseAdminConnection` (#638)
+  * implement overloads on `UpdateInstanceRequestBuilder` (#921)
+  * implement metadata decorator for `InstanceAdminStub`. (#678)
+  * implement logging wrapper for `InstanceAdminStub`. (#676)
+  * support install components for the library (#659)
+
+* **Bug fixes**
+  * fix runtime install directory (#658)
+  * give sample programs a long timeout time. (#622)
+  * use RunTransaction for read write transaction sample (#654)
+
+### v0.1.x - 2019-09
+* This is the initial Alpha release of the library.
+* While this version is not recommended for production workloads it is stable
+  enough to use in experimental code. We welcome feedback about the library
+  through [GitHub issues](https://github.com/googleapis/google-cloud-cpp-spanner/issues/new).
+* The API is expected to undergo incompatible changes before Beta and GA.
+* The library supports all the operations to read and write data into Cloud
+  Spanner.
+* The library supports some administrative operations such as creating,
+  updating, and dropping databases.