Update turn-howto.rst to use git clone (2)

Not logical to use svn checkout against a github repo, so changed to git clone. 

Signed-off-by: Rick Cogley <rick.cogley@esolia.co.jp>

docs/turn-howto.rst

@@ -19,18 +19,21 @@ coturn Setup
 You may be able to setup coturn via your package manager,  or set it up manually using the usual ``configure, make, make install`` process.  
 
  1. Check out coturn::
+ 
       git clone https://github.com/coturn/coturn.git coturn
       cd coturn
 
  2. Configure it::
+ 
       ./configure
 
-    You may need to install libevent2: if so, you should do so
+    You may need to install ``libevent2``: if so, you should do so
     in the way recommended by your operating system.
     You can ignore warnings about lack of database support: a
     database is unnecessary for this purpose.
 
  3. Build and install it::
+ 
       make
       make install
 
@@ -55,6 +58,7 @@ You may be able to setup coturn via your package manager,  or set it up manually
     import your private key and certificate.
 
  7. Start the turn server::
+ 
        bin/turnserver -o