added user and group for the example app
added user and group for the example app

if either user or group is missing, the actool validation would remind it's required:

$ actool -debug validate manifest.json
manifest.json: invalid ImageManifest: User is required
manifest.json: invalid ImageManifest: Group is required

Signed-off-by: Derek Ch <9005d0112f8b7a9031d4722bf4b49b99662ccb21@gmail.com>
fdserr/rkt,euank/rkt,luebken/rkt,xnox/rkt,Wilybald/rkt,kinvolk/rkt,ramitsurana/rkt,liubq919/rkt,sinfomicien/rkt,Shashwatsh/rkt,kbrwn/rkt,eyakubovich/rkt,yifan-gu/rkt,Yhgenomics/rkt,akshaykarle/rkt,coreos/rkt,sinfomicien/rkt,iaguis/rkt,linki/rkt,shtouff/rkt,lsm5/rkt,nhlfr/rkt,squeed/rkt,crawford/rkt,iankronquist/rkt,alexhersh/rkt,jonboulle/rkt,mattthias/pkg-rkt,mike1729/rkt,ramitsurana05/rkt,tixxdz/rkt,intfrr/rkt,blixtra/rkt,euank/rkt,mattthias/pkg-rkt,rkt/rkt,s-urbaniak/rkt,matthaias/rkt,Shashwatsh/rkt,jjlakis/rkt,alban/rkt,ybubnov/rkt,clearlinux/rkt,markllama/rkt,blixtra/rkt,Yhgenomics/rkt,euank/rkt,robszumski/rocket,rhvgoyal/rkt,klizhentas/rkt,MattDees/rkt,yifan-gu/rkt,eyakubovich/rkt,wparad/rkt,mjg59/rkt,fdserr/rkt,dalanlan/rkt,joshix/rkt,joshix/rkt,klizhentas/rkt,ybubnov/rkt,joshix/rkt,akshaykarle/rkt,intelsdi-x/rkt,chrisseto/rkt,Wilybald/rkt,shobhit85/rkt,il9ue/rkt,luebken/rkt,endocode/rkt,yifan-gu/rkt,fdserr/rkt,Wilybald/rkt,squeed/rkt,lee212/rkt,lucasallan/rkt,smarvin/rkt,ramitsurana05/rkt,adfernandes/rkt,jzelinskie/rkt,ramitsurana05/rkt,MattDees/rkt,akshaykarle/rkt,s-urbaniak/rkt,yifan-gu/rocket,jakon89/rkt,cab105/rkt,squeed/rkt,jjlakis/rkt,jakon89/rkt,tixxdz/rkt,MabinGo/rkt,smarvin/rkt,endocode/rkt,smarvin/rkt,lucasallan/rkt,crawford/rkt,mattthias/pkg-rkt,mjg59/rkt,alexhersh/rkt,dgonyeo/rkt,xnox/rkt,sgotti/rkt,ramitsurana/rkt,maquanyi/rkt,marineam/rkt,alban/rkt,coreos/rkt,kinvolk/rkt,joshix/rkt,markllama/rkt,rot26/rkt,maquanyi/rkt,Shashwatsh/rkt,kbrwn/rkt,achanda/rkt,robszumski/rocket,MattDees/rkt,liubq919/rkt,yifan-gu/rocket,krnowak/rkt,sstabellini/rkt,kinvolk/rkt,iaguis/rkt,monstermunchkin/rkt,tv42/rkt,coreos/rkt,tv42/rkt,rkt/rkt,mjg59/rkt,kbrwn/rkt,marineam/rkt,tmrts/rkt,dalanlan/rkt,nhlfr/rkt,wparad/rkt,rkt/rkt,maquanyi/rkt,bsmr-go/rkt,alexhersh/rkt,robszumski/rocket,rkt/rkt,s-urbaniak/rkt,jjlakis/rkt,Yhgenomics/rkt,chrisseto/rkt,chrisseto/rkt,bsmr-go/rkt,liugenping/rkt,adfernandes/rkt,monstermunchkin/rkt,squaremo/rkt,michelangelo13/rkt,jonboulle/rkt,tv42/rkt,lsm5/rkt,squaremo/rkt,liubq919/rkt,liugenping/rkt,MabinGo/rkt,rhvgoyal/rkt,intelsdi-x/rkt,bsmr-go/rkt,rot26/rkt,sgotti/rkt,achanda/rkt,ChengTiesheng/rkt,linki/rkt,cab105/rkt,intelsdi-x/rkt,michelangelo13/rkt,ramitsurana/rkt,dgonyeo/rkt,matthaias/rkt,mike1729/rkt,jasonchaffee/rkt,kinvolk/rkt,lucasallan/rkt,intfrr/rkt,ybubnov/rkt,linki/rkt,adfernandes/rkt,cab105/rkt,dalanlan/rkt,tmrts/rkt,iankronquist/rkt,shobhit85/rkt,lee212/rkt,wparad/rkt,marineam/rkt,lee212/rkt,lucasallan/rkt,xnox/rkt,yifan-gu/rocket,ChengTiesheng/rkt,rhvgoyal/rkt,jzelinskie/rkt,ChengTiesheng/rkt,lsm5/rkt,sinfomicien/rkt,sstabellini/rkt,monstermunchkin/rkt,nhlfr/rkt,iankronquist/rkt,achanda/rkt,alban/rkt,il9ue/rkt,shobhit85/rkt,liugenping/rkt,jonboulle/rkt,klizhentas/rkt,shtouff/rkt,matthaias/rkt,il9ue/rkt,luebken/rkt,crawford/rkt,jakon89/rkt,MabinGo/rkt,sgotti/rkt,eyakubovich/rkt,shtouff/rkt,michelangelo13/rkt,clearlinux/rkt,Wilybald/rkt,markllama/rkt,mike1729/rkt,tixxdz/rkt,blixtra/rkt,endocode/rkt,tmrts/rkt,krnowak/rkt,jzelinskie/rkt,sstabellini/rkt,iaguis/rkt,intfrr/rkt,krnowak/rkt,jasonchaffee/rkt,rot26/rkt,clearlinux/rkt,squaremo/rkt,jasonchaffee/rkt,dgonyeo/rkt