add XML support

fix unicode issue
allow disabling deep results per-request

originally by @johaness
allow fine grained control of relations included in output
bump to 1.current-upstream-version
support deep parameter in PUT/PATCH

follow up to d85b91e0d5d133ddb989d31ce98ae4f385d2432f and dc06ae4ae75994d354db8bbe62532bd04da0b5ac
search: joined load of all deep relations
limit joins to 3 levels
bump version number to Major.minor.revision.2
Raise exception for bad searches

... so that we can register an error handler in Flask to show
helpful response messages to API consumers
Support Python 3.3
bump version number to Major.minor.revision.3
Reraise `deep`-related json parsing exceptions as BadRequest
bump version number to Major.minor.revision.4
bump version number to Major.minor.revision.5
bump version number to Major.minor.revision.6
add `flat` parameter as opposite of `deep`
bump version number to Major.minor.revision.7
bump version number to Major.minor.revision.8
allow classes to modify ex-/include columns per serialization
bump version number to Major.minor.revision.9