request Content-Type now ignores charset if defined in the header

closes #20
references #9
Merge branch '3.3/feature/20-request-content-type-charset' into 3.3/develop
reworder error message
restored unnecessarily removed response object
if response content type not determined yet throw a simple exception
corrected action_invalid() to make correct use of Kohana 3.3 HTTP Exceptions
Merge branch '3.3/develop' into 3.3/feature/17-error-handling-bugfixes
removed module's HTTP_Exception and replaced all RESTful_HTTP_Exception::factory() with HTTP_Exception::factory()
minor code comment update
minor tweak for handling response body in text/plain
error response body is now handled via restful view and some logic within it

addresses #17
Merge branch '3.3/feature/17-error-handling-bugfixes' into 3.3/develop
added execute() method that throws 405 instead of the default 404
moved action checks and setting to RESTful_Core::route_filter() to be used when filtering api request routes

closes #19
Merge branch '3.3/feature/19-configurable-action-map' into 3.3/develop
Merge branch '3.3/develop' into 3.3/feature/18-readme-update