editor: add ^W delete word binding

It allows to delete the current word (any string of characters until a
space). Also, all spaces at the start are cleared to allow doing
something like:

    Hello world|
    Hello | <- the cursor is at a space
    | <- nothing left

1 files changed, 4 insertions, 0 deletions

diff --git a/ui/ui.go b/ui/ui.go
index e527f8e..50ddab5 100644
--- a/ui/ui.go
+++ b/ui/ui.go
@@ -192,6 +192,10 @@ func (ui *UI) InputDelete() (ok bool) {
 	return ui.e.RemRuneForward()
 }
 
+func (ui *UI) InputDeleteWord() (ok bool) {
+	return ui.e.RemWord()
+}
+
 func (ui *UI) InputAutoComplete(offset int) (ok bool) {
 	return ui.e.AutoComplete(offset)
 }