Add option to match newline in avy-goto-char-timer

Fixes #220
Fixes #225

avy.el

@@ -1768,6 +1768,10 @@ newline."
 
 (defcustom avy-timeout-seconds 0.5
   "How many seconds to wait for the second char."
+  :type 'float)
+
+(defcustom avy-enter-times-out t
+  "Whether enter exits avy-goto-char-timer early. If nil it matches newline"
   :type 'boolean)
 
 (defun avy--read-candidates (&optional re-builder)
@@ -1802,7 +1806,9 @@ Otherwise, the whole regex is highlighted."
                (delete-overlay ov))
              (setq overlays nil)
              (cond
-               ;; Handle RET
+               ;; Handle RET
+               ((= char 13)
+                (if avy-enter-times-out
                     (setq break t)
                   (setq str (concat str (list ?\n)))))
                ;; Handle C-h, DEL