Updated documentation

* Added paragraph and example about returning tuples from a filter
  (Issue #859)

* Added section about manualpois
  (Issue #858, Issue #869, Issue #598)

* Fixed a typo in the FAQ

* Added logging to file to the FAQ
  (Issue #871)

docs/faq.rst

@@ -38,7 +38,7 @@ of the following:
   Map expansions double the width and height of the map, so you will eventually
   hit a map size that is unlikely to need another level.
 
-You've added a few feature or changed textures, but it's not showing up on my map!
+You've added a new feature or changed textures, but it's not showing up on my map!
 ----------------------------------------------------------------------------------
 
 Some new features will only show up in newly-rendered areas. Use the
@@ -91,6 +91,21 @@ If you are seeing exorbitant memory usage, then it is likely either a bug or a
 subtly corrupted world. Please file an issue or come talk to us on IRC so we can
 take a look! See :ref:`help`.
 
+How can I log The Overviewer's output to a file?
+------------------------------------------------
+
+If you are on a UNIX-like system like MacOSX or Linux, you can use shell redirection
+to write the output into a file::
+
+    overviewer.py --config=myconfig.py > renderlog.log 2>&1
+
+What this does is redirect the previous commands standard output to the file "renderlog.log",
+and redirect the standard error to the standard output. The file will be overwritten each time
+you run this command line; to simply append the output to the file, use two greater than signs::
+
+    overviewer.py --config=myconfig.py >> renderlog.log 2>&1
+
+
 .. _cropping_faq:
 
 I've deleted some sections of my world but they still appear in the map