DOC: added note to docstring of numpy.savez
DOC: added note to docstring of numpy.savez

Note indicates that when used with dictionaries, savez will remove
leading "/" in dictionary keys.
See #9265

jorisvandenbossche/numpy,simongibbons/numpy,abalkin/numpy,charris/numpy,endolith/numpy,jorisvandenbossche/numpy,simongibbons/numpy,endolith/numpy,rgommers/numpy,pdebuyl/numpy,mhvk/numpy,mhvk/numpy,numpy/numpy,seberg/numpy,numpy/numpy,rgommers/numpy,charris/numpy,seberg/numpy,pbrod/numpy,jakirkham/numpy,endolith/numpy,pbrod/numpy,WarrenWeckesser/numpy,madphysicist/numpy,anntzer/numpy,abalkin/numpy,mhvk/numpy,seberg/numpy,grlee77/numpy,abalkin/numpy,grlee77/numpy,seberg/numpy,mattip/numpy,jakirkham/numpy,charris/numpy,jakirkham/numpy,madphysicist/numpy,pdebuyl/numpy,WarrenWeckesser/numpy,mattip/numpy,jakirkham/numpy,numpy/numpy,grlee77/numpy,numpy/numpy,pbrod/numpy,rgommers/numpy,jorisvandenbossche/numpy,WarrenWeckesser/numpy,madphysicist/numpy,anntzer/numpy,endolith/numpy,rgommers/numpy,simongibbons/numpy,mattip/numpy,mhvk/numpy,WarrenWeckesser/numpy,jorisvandenbossche/numpy,mattip/numpy,mhvk/numpy,madphysicist/numpy,madphysicist/numpy,anntzer/numpy,WarrenWeckesser/numpy,charris/numpy,pbrod/numpy,jorisvandenbossche/numpy,grlee77/numpy,pdebuyl/numpy,simongibbons/numpy,simongibbons/numpy,pdebuyl/numpy,anntzer/numpy,grlee77/numpy,pbrod/numpy,jakirkham/numpy