Fix regression errors.

- Throw exceptions when returning a content type of debug/*.
- Fix notice when constructing the request.
Merge branch 'master' of github.com:vanilla/garden
Change the way Request::defaultEnvironment() works.

- You now pass an array as the $key argument to set the default environment.
- Added the $merge parameter to specify merging vs. overwriting the default environment.
Change the way internal application runs work.

- Add an Accept header value of application/internal to represent requests that don’t render to the browser.
- Add support for X-Asset header and Response->asset() to change the data that is returned.
- Add Response->meta() to add a data store for separate meta information.