Convert fenced code blocks to Kramdown style

docs/ivanx/a2server_commands.md

@@ -35,7 +35,7 @@ Once logged in, you can enter the following commands.
 typing `a2server-setup`, answering "no" to all prompts if you like.)
 
 
-```
+~~~
 A2SERVER commands:
   (note: new commands may be added; use a2server-setup to refresh)
 
@@ -122,7 +122,7 @@ mkatinit: set up network boot configuration files
 cppo: catalog and copy files from ProDOS image file (slow, but works)
   (add -h to show help for the above four commands, e.g. "afptype -h")
 
-```
+~~~
 
 
 [1]: http://support.apple.com/kb/dl999

docs/ivanx/a2server_installubuntu.md

@@ -44,9 +44,10 @@
 
 * If you installed Debian rather than Ubuntu, type:
   
-  ```
+  ~~~
   sudo sed -i '0,/-eq 0/s/-eq 0/-ge 0/' /etc/profile
-  ```
+  ~~~
+  {: .language-bash}
 
 * When you're back at the prompt, type `sudo shutdown -h now` which
   will turn off the (virtual) machine.

docs/ivanx/a2server_netboot.md

@@ -7,9 +7,10 @@ running from "bare metal" if you wanted to.
 
 To do this, [log into the a2server console](a2server_commands.md), and type:
 
-```
+~~~
 a2server-setup
-```
+~~~
+{: .language-bash}
 
 After confirming that you want to proceed, you will be asked if you want to
 set up A2SERVER for network boot. Just follow the prompts. If you elect to

docs/ivanx/a2server_recovery.md

@@ -65,9 +65,11 @@ _A2SERVER on Raspberry Pi without screen/keyboard mouse, and a Linux computer_
 * Remove the SD card from your Pi.
 
 * On your Linux computer, type:
-  ```
+  
+  ~~~
   wget ivanx.com/a2server/fix; source fix
-  ```
+  ~~~
+  {: .language-bash}
 
 * Follow the on-screen instructions.
 
@@ -90,9 +92,11 @@ computer_
   password "apple2".
 
 * In the virtual machine window, type:
-  ```
+
+  ~~~
   wget ivanx.com/a2server/fix;source fix
-  ```
+  ~~~
+  {: .language-bash}
 
 * Follow the on-screen instructions.