Updated README to point to latest release.
Fix examples id

id field doesn't support upper case character.

Signed-off-by: Chengwei Yang <yangchengwei@qiyi.com>
Merge pull request #409 from chengweiv5/master

Fix examples id
Merge branch '0.7.0-preview' of github.com:mesosphere/marathon into 0.7.0-preview
removed usages of global ExecutionContext