Remove test message and clean up live export

remove message
make eww situation more obvious
clarify note on eww

[jrblevin@sdf.org: Five commits squashed and rebased on master]
Signed-off-by: Jason Blevins <jrblevin@sdf.org>

markdown-mode.el

@@ -5146,11 +5146,11 @@ buffer. Inverse of `markdown-live-preview-buffer'.")
 
 (defun markdown-live-preview-window-eww (file)
   "A `markdown-live-preview-window-function' for previewing with eww."
-  (if (eval-when-compile (featurep 'eww))
+  (if (featurep 'eww)
       (progn
         (eww-open-file file)
         (get-buffer "*eww*"))
-    (error "eww is not present on this version of emacs")))
+    (error "eww is not present or not loaded on this version of emacs")))
 
 (defun markdown-live-preview-window-serialize (buf)
   "Get window point and scroll data for all windows displaying BUF if BUF is

tests/markdown-test.el

@@ -3227,7 +3227,6 @@ indented the same amount."
     (unless (featurep 'eww)
       (should-error (markdown-live-preview-mode)))
     (markdown-temp-eww
-     (message "%s" "hey")
      (markdown-live-preview-mode)
      (should (buffer-live-p markdown-live-preview-buffer))
      (should (eq (current-buffer)