Handling error_subcode field in error responses

Most of the OAuth errors also return an error_subcode field. Different subcodes require
different recovery tactic, as defined in Facebook's reference:
https://developers.facebook.com/docs/reference/api/errors/

The implementation breaks binary compatibility, as the signature of
FacebookExceptionMapper.exceptionForTypeAndMessage was changed.
Merge pull request #59 from egergo/error-subcode

Handling error_subcode field in error responses
Added comment reply fields (+ breaking changes fixes july 2013)
Added field 'id' to Venue class for issue # 65
fix for null pointer exception while converting JSON string to Post object.
Merge pull request #66 from sbisht/master

Fix for issue #65
Formatting cleanups
Added undocumented fields to Event type
Merge pull request #63 from pjsb/master

Added comment reply fields (+ breaking changes fixes july 2013)
Updated CHANGELOG
fixes #86 added allow field in the Privacy object
Merge pull request #87 from tsuijten/master

fixes #86 added allow field in the Privacy object
Merge branch 'master' of https://github.com/revetkn/restfb