Fix a couple of documentation issues

* Warnings by sphinx (title underline too short)
* Example in documentation for the `Sound` class

Author: ddemidov

README.rst

@@ -198,7 +198,7 @@ The ev3dev-lang Project on GitHub
     would normally need to access this information.
 
 Python 2.x and Python 3.x Compatibility
--------------------------------------
+---------------------------------------
 
 Some versions of the ev3dev_ distribution come with both `Python 2.x`_ and `Python 3.x`_ installed
 but this library is compatible only with Python 3.

docs/faq.rst

@@ -2,7 +2,7 @@ Frequently-Asked Questions
 ==========================
 
 My script works when launched as ``python3 script.py`` but exits immediately or throws an error when launched from Brickman or as ``./script.py``
------
+-------------------------------------------------------------------------------------------------------------------------------------------------
 
 This may occur if your file includes Windows-style line endings, which are often
 inserted by editors on Windows. To resolve this issue, open an SSH session and

ev3dev/core.py

@@ -2956,13 +2956,14 @@ class Sound:
     immediately after child process was spawned, without waiting for its
     completion), but you can call wait() on the returned result.
 
-    Examples:
+    Examples::
 
         # Play 'bark.wav', return immediately:
         Sound.play('bark.wav')
 
         # Introduce yourself, wait for completion:
         Sound.speak('Hello, I am Robot').wait()
+
     """
 
     @staticmethod