update CREDITS file to include Yan and Dave
update CREDITS file to include Yan and Dave

stupidcache/psutil,kiranvizru/psutil,Alwnikrotikz/psutil,kiranvizru/psutil,tigerneil/psutil,skyshe/psutil,skyshe/psutil,AlanZatarain/psutil,zhengzheng/psutil,tigerneil/psutil,creativewild/psutil,google-code-export/psutil,end18/psutil,PFZheng/psutil,marmolu/psutil,end18/psutil,PFZheng/psutil,stupidcache/psutil,marmolu/psutil,djhaskin987/psutil,peter-hst/psutil,creativewild/psutil,djhaskin987/psutil,skyshe/psutil,huson2012/psutil,kiranvizru/psutil,nmani1905/psutil,huson2012/psutil,vmolsa/psutil,huson2012/psutil,skyshe/psutil,shiva21/psutil,chjwang/psutil,jucapj/psutil,nmani1905/psutil,peter-hst/psutil,kiranvizru/psutil,vmolsa/psutil,jucapj/psutil,shiva21/psutil,creativewild/psutil,vmolsa/psutil,end18/psutil,google-code-export/psutil,djhaskin987/psutil,tigerneil/psutil,google-code-export/psutil,stupidcache/psutil,Alwnikrotikz/psutil,anfedorov/psutil,tigerneil/psutil,end18/psutil,anfedorov/psutil,vmolsa/psutil,chjwang/psutil,djhaskin987/psutil,google-code-export/psutil,AlanZatarain/psutil,zhengzheng/psutil