Fixes unsafe pointer madness.

`func uiEvt(e termbox.Event) Event` used to change the type of termbox.Event to Event by
using some pointer-cast magic[1], which could cause an overflow if `termbox.Event` changes
its structure.
I'd rather just have `type Event termbox.Event` but that would break backwards compatibility.

Warning: A buffer overflow could cause a serious security issue but it is very unlikely that
anyone could exploit that (though not impossbible). You'd need to push a upstream update to
termbox, which would tweak termbox.Event's structure. Still, this issue should be fixed and
unsafe should never be used.

[1] it used to get the address of termbox.Event and just cast a Event pointer

events.go

@@ -9,7 +9,6 @@
 package termui
 
 import "github.com/nsf/termbox-go"
-import "unsafe"
 
 /***********************************termbox-go**************************************/
 
@@ -133,7 +132,19 @@ const (
 
 // convert termbox.Event to termui.Event
 func uiEvt(e termbox.Event) Event {
-	return *(*Event)(unsafe.Pointer(&e))
+	event := Event{}
+	event.Type = EventType(e.Type)
+	event.Mod = Modifier(e.Mod)
+	event.Key = Key(e.Key)
+	event.Ch = e.Ch
+	event.Width = e.Width
+	event.Height = e.Height
+	event.Err = e.Err
+	event.MouseX = e.MouseX
+	event.MouseY = e.MouseY
+	event.N = e.N
+
+	return event
 }
 
 var evtChs = make([]chan Event, 0)