clean up userguide/limitations.rst, let it refer to the bug tracker
clean up userguide/limitations.rst, let it refer to the bug tracker

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