2014-03-29: wisp-mode: line with only underscores and whitespace shown as

wisp-mode: line with only underscores and whitespace shown as default text.

diff --git a/wisp-mode.el b/wisp-mode.el
--- a/wisp-mode.el
+++ b/wisp-mode.el
@@ -74,6 +74,7 @@
   `((
      ("\\`#!.*" . font-lock-comment-face) ; initial hashbang
      ("\"\\.\\*\\?" . font-lock-string-face) ; strings (anything between "")
+     ("^_+ *$" . font-lock-default-face) ; line with only underscores and whitespace shown as default text.
      ("^\\(?:_* +\\| *\\): *$" . font-lock-keyword-face) ; line with only a : + whitespace, not at the beginning
      ("^\\(?:_* +\\| *\\): \\| *\\. " . font-lock-keyword-face) ; leading : or .
      ( ,(regexp-opt wisp-builtin 'symbols) . font-lock-builtin-face) ; generic functions