Add Chef 15.1 release notes
Add Chef 15.1 release notes

Add the release notes for Chef 15.1

Signed-off-by: Tim Smith <764ef62106582a09ed09dfa0b6bff7c05fd7d1e4@chef.io>

MsysTechnologiesllc/chef,higanworks/chef,mwrock/chef,chef/chef,MsysTechnologiesllc/chef,higanworks/chef,tas50/chef-1,chef/chef,mwrock/chef,tas50/chef-1,nvwls/chef,jaymzh/chef,nvwls/chef,gene1wood/chef,mattray/chef,mattray/chef,mwrock/chef,gene1wood/chef,gene1wood/chef,tas50/chef-1,tas50/chef-1,chef/chef,higanworks/chef,mwrock/chef,chef/chef,jaymzh/chef,higanworks/chef,higanworks/chef,jaymzh/chef,MsysTechnologiesllc/chef,nvwls/chef,MsysTechnologiesllc/chef,mattray/chef,mattray/chef,gene1wood/chef,nvwls/chef,nvwls/chef,nvwls/chef,jaymzh/chef,mattray/chef