Mention that Router.current() is reactive

And add example of using `this.path`
Merge pull request #590 from dandv/patch-1

Mention that Router.current() is reactive
Remove erroneous executable permssion on js files.
Fix up route error messages and url func.
Set layout before each recomputed action; closes #600
Bump blaze-layout version and minor pr/607 adjustments.

- We want to fix the setLayout(undefined) issue in blaze-layout itself, rather
  than relying on an OR guard inside of iron-router.
Merge branch 'dev' of github.com:EventedMind/iron-router into dev