Add a config for circle.yml

Change-Id: I30a3d8ffb7f1316ee793902865813d895ef08dd9
Use the right syntax.

Change-Id: Ice569c4b22d68aada4e5262c5c913f1cb7e3e861
And don't exclude non-existent tasks.

Change-Id: I6403ff3ab6c96a10c380646152571603ae3b83fb
Merge pull request #2 from csmith/master

Add circle.yml config.