Add support for arguments in __bashum_run_n()

People can now run

    __bashum_run_n 100 echo hello world

and it will print "hello world" 100 times, instead of just running
`echo` 100 times and ignoring the `hello world` part.

dotfiles/bash/main.bashrc

 
 __bashum_run_n() {
     #
-    # Run $2 in background $1 times
+    # Run $2.. in background $1 times
     #
-    local n=${1:-1}
+    local n=${1:-1}; shift
     while test "$n" -gt 0;
     do
-        "$2" &
+        "$@" &
         ((n--))
     done
 }