Fixed quotes

Signed-off-by: Marcus Noble <github@marcusnoble.co.uk>

home/.dotfiles/aliases

@@ -10,9 +10,9 @@ alias _find=`which find`
 alias _top=`which top`
 alias _ps="/bin/ps"
 alias _dig=`which dig`
-alias _readlink=`/usr/bin/readlink`
-alias _sed=`/usr/bin/sed`
-alias _date=`/bin/date`
+alias _readlink='/usr/bin/readlink'
+alias _sed='/usr/bin/sed'
+alias _date='/bin/date'
 alias _git=`which git`
 if command -v $(brew --prefix)/bin/git &>/dev/null; then
   alias _git=$(brew --prefix)/bin/git