Add a :VimPreview command

[xuhdev]

Add such a command would make it less possible to conflict with existing key maps. (<Leader>p is too simple) Users could map it to whatever if they want. For backward compatibility, I recommend to add a option to disable the default <Leader>p key mapping. By default, the key mapping is enabled.

[greyblake]

OK. Tnx for the suggestion. I've got an injury. Will fix it latter.