Bump version to v1.2.1

Signed-off-by: Dong Chen <dongluo.chen@docker.com>

CHANGELOG.md

@@ -1,6 +1,10 @@
 # Changelog
 
-## 1.2.1 (2016-04-22)
+## 1.2.1 (2016-05-03)
+
+#### Scheduler
+
+- Add containerslots filter to allow user to limit container number on a node
 
 #### API
 
@@ -10,16 +14,27 @@
 - Return an error when assertion fails in hijack
 - Return an error when Image Pull fails
 - Fix image pull bug (wait until download finishes)
+- Fix and document some api response status codes
+- Add NodeID in docker info
+- Support docker ps --filter by volume
 
 #### Build
 
-- Switch to go 1.6.2
 - Move dependencies to vendor/
 - Update Image Pull to use docker/distribution package
+- Convert docs Dockerfiles to use docs/base:oss
+
+#### Test
+
+- Fix api/ps tests
+- Update api/stats test to prevent timeout on master branch
+- Use --cpu-shares instead of -c in integration test
 
 #### Misc
 
 - Documentation clean up
+- Close http response body to avoid potential memory leak
+- Switch context.TODO() to context.Background() to enable context setting
 
 ## 1.2.0 (2016-04-13)