Add python-markdown in list of requirements

That removes an extra hurdle for people trying
to contribute to source.android.com

Change-Id: I5dc457b550f1101ea0e78ca9dd23118c24f9da39
diff --git a/src/source/initializing.md b/src/source/initializing.md
index d394c4f..fdc3f63 100644
--- a/src/source/initializing.md
+++ b/src/source/initializing.md
@@ -69,7 +69,7 @@
     $ sudo apt-get install git-core gnupg flex bison gperf build-essential \
       zip curl zlib1g-dev libc6-dev lib32ncurses5-dev ia32-libs \
       x11proto-core-dev libx11-dev lib32readline5-dev lib32z-dev \
-      libgl1-mesa-dev g++-multilib mingw32 tofrodos
+      libgl1-mesa-dev g++-multilib mingw32 tofrodos python-markdown
 
 ## Configuring USB Access ##