Update visual_metrics.py arguments; genericize Python interpreter.

Change-Id: I74e70509e0d756e9de0ca40cffc86fd0dc7bb12c
modified:   scripts/visual_metrics.py
modified:   webm-contributor-guide.txt
diff --git a/scripts/visual_metrics.py b/scripts/visual_metrics.py
index efda5a1..f6fe8f1 100755
--- a/scripts/visual_metrics.py
+++ b/scripts/visual_metrics.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python2.4
+#!/usr/bin/python
 #
 # Copyright 2010 Google Inc.
 # All Rights Reserved.
diff --git a/webm-contributor-guide.txt b/webm-contributor-guide.txt
index 6fbb7a0..1ac04e0 100644
--- a/webm-contributor-guide.txt
+++ b/webm-contributor-guide.txt
@@ -38,7 +38,7 @@
 -----------------
 
   * A Bash shell
-  * Python 2.4
+  * Python
   * A modern web browser (like Google Chrome)
 
 
@@ -127,7 +127,7 @@
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      $ git clone http://git.chromium.org/webm/libvpx.git
      $ cd libvpx
-     $ git checkout experimental
+     $ git checkout -b experimental origin/experimental
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      </div>
 
@@ -183,7 +183,7 @@
      an **HTML-format report** that compares `mytweak` with `baseline`.
 
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-     $ visual_metrics.py . baseline mytweak > mytweak.html
+     $ visual_metrics.py "*stt" baseline mytweak > mytweak.html
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
   7. **View the report** by opening `mytweak.html` in a web browser.