add Router.all() method

Similar to app.all() but specifically for attaching handlers to all
methods under a standalone router. This is useful for isolating routers
that require "middleware" like features for all routes managed by the
router.
Removed Buffer call with 'binary' encoding option in auth example.

According to the Node.js documentation for Buffer objects regarding the
'binary' encoding option:

"This encoding method is deprecated and should be avoided in favor of
Buffer objects where possible. This encoding will be removed in future
versions of Node."

Simply calling toString() with a 'base64' argument on the hash seems to
accomplish the same thing; this makes the code compatible with current
documentation as well as being a bit easier to follow.
Merge pull request #1822 from yakubori/auth-buffer-call-removal

Removed Buffer call with 'binary' encoding option in auth example.