update vim readme with new mappings and options

vim/autoload/himalaya/mbox.vim

@@ -70,7 +70,11 @@ function! himalaya#mbox#pick(cb)
   endtry
 endfunction
 
-function! himalaya#mbox#set(mbox)
+function! himalaya#mbox#change()
+  call himalaya#mbox#pick("himalaya#mbox#_change")
+endfunction
+
+function! himalaya#mbox#_change(mbox)
   let s:curr_mbox = a:mbox
   let s:curr_page = 0
   call himalaya#msg#list()

vim/autoload/himalaya/msg.vim

@@ -147,7 +147,11 @@ function! himalaya#msg#forward()
   endtry
 endfunction
 
-function! himalaya#msg#copy(target_mbox)
+function! himalaya#msg#copy()
+  call himalaya#mbox#pick("himalaya#msg#_copy")
+endfunction
+
+function! himalaya#msg#_copy(target_mbox)
   try
     let pos = getpos(".")
     let msg_id = stridx(bufname("%"), "Himalaya messages") == 0 ? s:get_focused_msg_id() : s:msg_id
@@ -162,7 +166,11 @@ function! himalaya#msg#copy(target_mbox)
   endtry
 endfunction
 
-function! himalaya#msg#move(target_mbox)
+function! himalaya#msg#move()
+  call himalaya#mbox#pick("himalaya#msg#_move")
+endfunction
+
+function! himalaya#msg#_move(target_mbox)
   try
     let msg_id = stridx(bufname("%"), "Himalaya messages") == 0 ? s:get_focused_msg_id() : s:msg_id
     let choice = input(printf("Are you sure you want to move the message %d? (y/N) ", msg_id))

vim/autoload/himalaya/shared/bindings.vim

@@ -2,7 +2,7 @@ function! himalaya#shared#bindings#define(bindings)
   for [mode, key, name] in a:bindings
     let plug = substitute(name, "[#_]", "-", "g")
     let plug = printf("<plug>(himalaya-%s)", plug)
-    execute printf("%snoremap <silent>%s :call himalaya#%s<cr>", mode, plug, name)
+    execute printf("%snoremap <silent>%s :call himalaya#%s()<cr>", mode, plug, name)
 
     if !hasmapto(plug, mode)
       execute printf("%smap <nowait><buffer>%s %s", mode, key, plug)