factor out dispatching on content type
move `quality` method into separate class

This should allow it to be used by exception handling
`select_representation` shouldn't care about `action` property
this isn't javascript
placeholder docs
refactor error handling
get rid of redundant encoding header

python 3 is utf-8 by default
no longer using `singledispatch` so remove from setup.py
change `ExceptionHandler` to `ExceptionDispatcher`
make app exception dispatcher match dispatcher and router
ExceptionDispatcher can take bindings in constructor
add silly header
newline
typo
force passing of representation info as kwargs
working __repr__ for bindings
pass kwargs to new exception handler
add some tests for choosing exception handler based on content type
rename error_handling to exception_dispatch
split `binding` module between `dispatch` and `exception_dispatch`