Squashed commit of the following:

commit 6bf9fe89f638aa1c5f29bd03168311e2097fc8ad
Author: Satnam Singh <satnam@google.com>
Date:   Fri Sep 26 10:23:16 2014 -0700

    Change error to warning during handling check.

commit c58090718309247ae3edd561a7e76d612acbd966
Author: Satnam Singh <satnam@google.com>
Date:   Fri Sep 26 10:21:41 2014 -0700

    Decapatalise fmt.Errorf error messages.

commit 3ecc5745d60b49b0b9b2573684cd27f34364cf3e
Author: Satnam Singh <satnam@google.com>
Date:   Fri Sep 26 10:19:15 2014 -0700

    Fix misunderstanding about when CanHandle fails.

commit adce0c5433946613890c28eec68c8b7798a45633
Author: Satnam Singh <satnam@google.com>
Date:   Fri Sep 26 10:13:32 2014 -0700

    Change the interface of CanHandle to return error information.
Merge branch 'master' of github.com:satnam6502/cadvisor