Correct typos in Readme.org

Readme.org

@@ -94,7 +94,7 @@ $ git clone https://github.com/yjwen/org-reveal.git
    within the Org file.
 
 #+BEGIN_SRC org
- #+REVEAL_ROOT: file:///d:/reveal.js
+,#+REVEAL_ROOT: file:///d:/reveal.js
 #+END_SRC
 
    Set your =REVEAL_ROOT= to the following URL, to use reveal.js from
@@ -385,15 +385,6 @@ $ git clone https://github.com/yjwen/org-reveal.git
  =my-preamble=, now we will define =my-preamble= in an Org-Babel
     source block, as illustrated below (invisible in the slides).
 
-#+BEGIN_SRC emacs-lisp :exports results :results silent
-  (defun my-preamble (info)
-    ""
-    "<p>
-  Thanks to Org-Babel, now we can embed preambles into Org document!
-  </p>")
-  
-#+END_SRC
-
     The =:exports results :result silent= options mark the source
     block to be evaluated at exporting and the evaluation result
     is omitted, so it won't disturb slide contents.
@@ -439,7 +430,7 @@ $ git clone https://github.com/yjwen/org-reveal.git
    styles after loading a theme.
 
 #+BEGIN_SRC org
- #+REVEAL_EXTRA_CSS: url-to-custom-stylesheet.css
+,#+REVEAL_EXTRA_CSS: url-to-custom-stylesheet.css
 #+END_SRC
 
 ** Extra Dependent Script
@@ -447,7 +438,7 @@ $ git clone https://github.com/yjwen/org-reveal.git
    Set =REVEAL_EXTRA_JS= to the url of extra reveal.js dependent
    script if necessary.
 #+BEGIN_SRC org
- #+REVEAL_EXTRA_JS: url-to-custom-script.js
+,#+REVEAL_EXTRA_JS: url-to-custom-script.js
 #+END_SRC
 
 ** Extra Slide attribute
@@ -461,7 +452,7 @@ $ git clone https://github.com/yjwen/org-reveal.git
 
    Add =num:nil= to =#+OPTIONS=
 #+BEGIN_SRC org
- #+OPTIONS: num:nil
+,#+OPTIONS: num:nil
 #+END_SRC
 
 ** Internal Links