Make manifest url reader accept both single and multiple manifests.
Add kubelet testing to integration test. Test that kubelet makes the requested containers. Check that the url manifest feature works.
Readability fixes & address review comments.
Several small fixes.
Merge pull request #229 from brendandburns/fix

Several small fixes.
Make integration test the manifest url feature. Make kubelet's docker pull command testable.
Added some tests
Merge pull request #213 from lavalamp/fix_manifest

Better fix of #212
Merge pull request #237 from brendandburns/tests

Added some tests