Fixed compile warnings with Cython 0.20

Ignore-this: d9af979c08ee87cc3111069f850aec1e

darcs-hash:20140204131843-56b4d-232ea090928550fb121fd53d51f1ba547d06d6df
Raised core version

Ignore-this: 83806effd39e155434fec5a2008408fe

darcs-hash:20140204152303-56b4d-fa8a32b9069645817a3962e41204b65122ccb368
Don't apply str() when calling SIPURI.parse

Ignore-this: c8250ad3ea4b27ea93a2d69e062f8a85

darcs-hash:20140204153936-56b4d-e64cf2df913bb6daa38c7d9dacfaa4d373e54929