revert cargo workspace feature

vim/plugin/himalaya.vim

@@ -1 +1,19 @@
-echoerr 'Cannot load himalaya: please change the rtp path from "vim" to "email-manager/vim" (https://github.com/soywod/himalaya/tree/development/email-manager/vim).'
+if exists("g:loaded_himalaya")
+  finish
+endif
+
+if !executable("himalaya")
+  throw "Himalaya CLI not found, see https://github.com/soywod/himalaya#installation"
+endif
+
+" Backup cpo
+let s:cpo_backup = &cpo
+set cpo&vim
+
+command! -nargs=* Himalaya call himalaya#msg#list(<f-args>)
+
+" Restore cpo
+let &cpo = s:cpo_backup
+unlet s:cpo_backup
+
+let g:loaded_himalaya = 1