Suggestion: clarify Masked and Readonly Paths

[Mashimiao]

There is not clearly requirement for Masked or Readonly Paths.
I think we must definitely define they must be absolute path or not in runtime spec.

[wking]

On Fri, Jun 24, 2016 at 02:31:48AM -0700, Ma Shimiao wrote:

I think we must definitely define they must be absolute path or not
in runtime spec.

This is related to a general need to specify the anchor for relative
paths 1. If there is a config.md-wide entry like:

Relative paths are interpreted relative to the directory holding
config.json.

Then having relative paths here (or in other places) seems
sufficiently well-defined to me.

 and the next two lines.

[hqhq]

Fixed by: #587