upgrade to grails 2.2.0
change JSON to GSON and request.JSON to request.GSON

clearer what's being used & means standard converters can be used alongside new ones
tidied boolean
failing test for #7
updated readme for JSON->GSON change
javadocs
fix a couple of in-use glitches

1. Something doesn't work when using property name syntax internally in GSON
2. HttpServletRequest.reader may not work with Gson if it's forward-only
failing test for #9
flush output stream after rendering
not necessary to declare controller when using @TestFor(Controller)
start of test for `as GSON` handling
removed debug code
got test for #9 running

still fails for Map as GSON
Map as GSON now works

Fixes #9
simple rest app
basic functional test
working functional test!
add web-app/WEB-INF cruft that seems to be necessary for anything to run
check content type on PUT or POST
do content type check with beforeInterceptor