Addressing @danpovey comments: svn is still a prerequisite; svn mirror is not...

Addressing @danpovey comments: svn is still a prerequisite; svn mirror is not maintained; version control paragraph in tutorial_code.dox rewritten.

src/doc/install.dox

@@ -24,11 +24,7 @@
 
  \section install_download  Dowloading Kaldi
 
-  We have now transitioned to
- GitHub for all future development.  We still intend to maintain a
- read-only Subversion mirror of the GitHub parent, located at SourceForge and mirrored
- by us.
-
+  We have now transitioned to GitHub for all future development.
   You first need to install Git. The most current version of Kaldi,
   possibly including unfinished and experimental features, can
    be downloaded by typing into a shell:

src/doc/tutorial_code.dox

@@ -169,25 +169,18 @@ If you need to debug a program that takes command-line arguments, you can do it
 \endverbatim
 or you can invoke gdb without arguments and then type "r arg1 arg2..." at the prompt.
 
-\todo This paragraph is full of lies!
 When you are done, and it compiles, type
 \verbatim
-svn diff
-\endverbatim
-to see what changes you made.  If you are contributing to the Kaldi project and you
-are planning to commit code in the near future, you
-may want to revert the changes you made so you don't accidentally commit them.  The following
-commands will save the file you modified in case you need it later, and will revert to
-the original version:
-\verbatim
- cp matrix-lib-test.cc matrix-lib-test.cc.tmp
- svn revert matrix-lib-test.cc
-\endverbatim
-If you actually wanted to commit the changes, and you had an account on Sourceforge, you
-would have to ask us to add you to the Kaldi project, and you would type something like
-\verbatim
-svn commit --username=your_sourceforge_username -m "Added a unit-test in matrix/ directory."
+ git diff
 \endverbatim
+to see what changes you made.  If you are contributing to the Kaldi project and
+planning to send us code in the near future, you
+may want to commit them to a branch as described in the \tutorial_git, so that you
+can generate a clean <a href="https://help.github.com/articles/using-pull-requests/">
+GitHub pull request</a> later. We recommend that you familiarize
+yourself with Git branches even if you are not contributing your changes
+outright; Git is a powerful tool to maintain your local code changes as well as
+those you may contribute.
 
 \section tutorial_code_acoustic Acoustic modeling code
 

src/doc/tutorial_prereqs.dox

@@ -47,7 +47,7 @@
   a different distribution of the RM data with a different layout.
 
   The system requirements are fairly basic.  We assume that you have tools
-  including wget, git, awk, perl and so on, or that you know how to install them.
+  including wget, git, svn, awk, perl and so on, or that you know how to install them.
   The most difficult part of the installation process relates to the math library
   ATLAS; if this is not already installed as a library on your system you will
   have to compile it, and this requires that CPU throttling be turned off, which