Add avandu-tt-rss-version command

Also add some doc fixes.

avandu.el

@@ -401,7 +401,7 @@ feeds."
   (avandu--next-button-of-type backward feed))
 
 (defun avandu-tt-rss-api-level ()
-  "Get the API level of the your Tiny Tiny RSS instance."
+  "Get the API level of your Tiny Tiny RSS instance."
   (interactive)
   (let ((level (cdr (assq 'level
                           (assq 'content
@@ -412,6 +412,18 @@ feeds."
 
     level))
 
+(defun avandu-tt-rss-version ()
+  "Get the version of your Tiny Tiny RSS instance."
+  (interactive)
+  (let ((version (cdr (assq 'version
+                            (assq 'content
+                                  (avandu--send-command
+                                   '((op . "getVersion"))))))))
+    (when (called-interactively-p 'any)
+      (message "Tiny Tiny RSS Version: %s" version))
+
+    version))
+
 ;; Overview
 (define-derived-mode avandu-overview-mode special-mode "Avandu:Overview"
   "Major mode fo the avandu overview screen.

doc/avandu.texinfo

@@ -250,6 +250,19 @@ interactively in any way it will print a message like:
 API Level: #
 @end example
 
+and it returns the api level as an integer.
+
 This does not currently serve any purpose, but it might be used in the
 future to determine which functions are available.
 @end deffn
+
+@deffn Command avandu-tt-rss-version
+Get the version of the Tiny Tiny RSS instance.  If called
+interactively in any way it will print a message like:
+
+@example
+Tiny Tiny RSS Version: #
+@end example
+
+and it returns the version as a string.
+@end deffn