Add missing "install" argument to yum command in README.md.
Add missing "install" argument to yum command in README.md.

Thanks to Paul Schulz <pschulz01@gmail.com> for pointing it out.

Signed-off-by: Rob Browning <1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org>

pombredanne/bup,gevaerts/bup,jbaber/bup,gevaerts/bup,jbaber/bup,tjanez/bup,mhoeher/bup,pombredanne/bup,mhoeher/bup,ToxicFrog/bup,tjanez/bup,apenwarr/bup,pombredanne/bup,ToxicFrog/bup,jbaber/bup,ToxicFrog/bup,mhoeher/bup,tjanez/bup,pombredanne/bup,ToxicFrog/bup,mhoeher/bup,tjanez/bup,pombredanne/bup,gevaerts/bup,mhoeher/bup,jbaber/bup,jbaber/bup,tjanez/bup,apenwarr/bup,pombredanne/bup,apenwarr/bup,mhoeher/bup,gevaerts/bup,apenwarr/bup,ToxicFrog/bup,gevaerts/bup,jbaber/bup,tjanez/bup