Fix sed errors on OSX, without breaking ubuntu

h/t @Keithbsmiley. Closes #125

z.sh

@@ -107,7 +107,7 @@ _z() {
             -*) local opt=${1:1}; while [ "$opt" ]; do case ${opt:0:1} in
                     c) local fnd="^$PWD $fnd";;
                     h) echo "${_Z_CMD:-z} [-chlrtx] args" >&2; return;;
-                    x) sed -i "\:^${PWD}|.*:d" "$datafile";;
+                    x) sed -i -e "\:^${PWD}|.*:d" "$datafile";;
                     l) local list=1;;
                     r) local typ="rank";;
                     t) local typ="recent";;