README.md: add a "bup init" step to "Using bup" since we killed auto-init.
README.md: add a "bup init" step to "Using bup" since we killed auto-init.

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

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