Added SetFocus() to Modal, focuses on the provided button. Resolves #364

modal.go

@@ -126,6 +126,12 @@ func (m *Modal) ClearButtons() *Modal {
 	return m
 }
 
+// SetFocus shifts the focus to the button with the given index.
+func (m *Modal) SetFocus(index int) *Modal {
+	m.form.SetFocus(index)
+	return m
+}
+
 // Focus is called when this primitive receives focus.
 func (m *Modal) Focus(delegate func(p Primitive)) {
 	delegate(m.form)

textview.go

@@ -298,8 +298,9 @@ func (t *TextView) SetRegions(regions bool) *TextView {
 
 // SetChangedFunc sets a handler function which is called when the text of the
 // text view has changed. This is useful when text is written to this io.Writer
-// in a separate goroutine. This does not automatically cause the screen to be
+// in a separate goroutine. Doing so does not automatically cause the screen to
-// refreshed so you may want to use the "changed" handler to redraw the screen.
+// be refreshed so you may want to use the "changed" handler to redraw the
+// screen.
 //
 // Note that to avoid race conditions or deadlocks, there are a few rules you
 // should follow: