Rework the context internals so that a context can see what the next handlers are.
Make it possible to add to the registry for downstream handlers as well as nested via next(*) methods.

Closes #183.
Expose the request ByteBuf.
Add getContext() to Context, which makes some things simpler.
Add an example for file uploading.
Document how content types are detected for handlebars templates.

Closes #131.
Merge remote-tracking branch 'origin/master'
Adding basic metric support
Adding basic metric support
Adding basic metric support - fixing dependency issue
Changes after code review
Basic metric support
Make this spec stepwise as the tests are order dependent.

This needs to be fixed.