Improve the C++ wrapping tutorial
Improve the C++ wrapping tutorial

Previously it didn't work if followed step by step (one has to link the
Rectangle.cpp file). This patch makes everything clear and explicit.

ChristopherHogan/cython,scoder/cython,fperez/cython,larsmans/cython,acrispin/cython,cython/cython,ABcDexter/cython,hpfem/cython,c-blake/cython,slonik-az/cython,hpfem/cython,fperez/cython,hhsprings/cython,hickford/cython,hickford/cython,encukou/cython,rguillebert/CythonCTypesBackend,fabianrost84/cython,larsmans/cython,ABcDexter/cython,andreasvc/cython,hpfem/cython,encukou/cython,da-woods/cython,encukou/cython,marscher/cython,encukou/cython,acrispin/cython,fperez/cython,c-blake/cython,madjar/cython,fperez/cython,marscher/cython,scoder/cython,scoder/cython,JelleZijlstra/cython,da-woods/cython,slonik-az/cython,roxyboy/cython,madjar/cython,mrGeen/cython,mrGeen/cython,rguillebert/CythonCTypesBackend,cython/cython,JelleZijlstra/cython,mcanthony/cython,andreasvc/cython,c-blake/cython,andreasvc/cython,encukou/cython,c-blake/cython,mrGeen/cython,achernet/cython,JelleZijlstra/cython,hhsprings/cython,rguillebert/CythonCTypesBackend,mcanthony/cython,hickford/cython,ChristopherHogan/cython,da-woods/cython,hhsprings/cython,rguillebert/CythonCTypesBackend,slonik-az/cython,dahebolangkuan/cython,andreasvc/cython,hpfem/cython,larsmans/cython,JelleZijlstra/cython,mrGeen/cython,scoder/cython,hickford/cython,madjar/cython,hhsprings/cython,madjar/cython,dahebolangkuan/cython,ABcDexter/cython,slonik-az/cython,cython/cython,madjar/cython,larsmans/cython,achernet/cython,hpfem/cython,acrispin/cython,achernet/cython,dahebolangkuan/cython,achernet/cython,acrispin/cython,slonik-az/cython,ABcDexter/cython,roxyboy/cython,ChristopherHogan/cython,JelleZijlstra/cython,fabianrost84/cython,marscher/cython,ABcDexter/cython,mrGeen/cython,fabianrost84/cython,hhsprings/cython,andreasvc/cython,larsmans/cython,fabianrost84/cython,c-blake/cython,cython/cython,fabianrost84/cython,mcanthony/cython,dahebolangkuan/cython,roxyboy/cython,roxyboy/cython,hickford/cython,da-woods/cython,marscher/cython,acrispin/cython,mcanthony/cython,roxyboy/cython,fperez/cython,marscher/cython,mcanthony/cython,dahebolangkuan/cython,achernet/cython