Add polyfill support for non-composer autoloading

- Ensure that if composer is not used for autoloading, polyfills are still
  required. See zendframework/zf2#3714 for details
Merge commit 'refs/pull/165/head' of github.com:zendframework/ZendSkeletonApplication

PR #165
Alternate precedence order for ZF2 path

- It makes more sense to assume that if ZF2 is actually _in_ the
  project, to use it, and only if not present start looking at the ENV
  and php.ini settings.
Merge branch '167'
Closes #167
Update ZF2 submodule to 2.1.3
Merge pull request #168 from aarbrown/zf213

Update ZF2 submodule to 2.1.3