fixed install command in readme
fixed install command in readme

elopio/snappy-playpen,ubuntu/snappy-playpen,elopio/snappy-playpen,elopio/snappy-playpen,jamestait/snappy-playpen,elopio/snappy-playpen,jamestait/snappy-playpen,jamestait/snappy-playpen,ubuntu/snappy-playpen,ubuntu/snappy-playpen,jamestait/snappy-playpen,ubuntu/snappy-playpen