communicate delay when opening external editor

[extrawurst]

right now only the spinner indicates that something is happening when opening the external editor which can take up to 2 seconds because the input polling needs to stop first.

see #46

[extrawurst]

done in de7f48f

[MartinVincent]

FYI: You can eliminate the wait if you immediately press Enter after launching the edit command.

ie:
place the cursor on a given file <<<< press 'e' to edit, then without waiting press 'Enter' and voilà, your file is editable in vim.

[extrawurst]

Yeah there must have been some fuckup when switching from the polling mechanism to the file-watcher. see #1506