ENH/BF: Workaround for stderr confusion after importing sounddevice

Fixes GH-2230.

Old behavior:
```
In [1]: from psychopy.sound import Sound
pygame 1.9.4
Hello from the pygame community. https://www.pygame.org/contribute.html

In [2]: input('foo> ')
bar.
Out[2]: 'bar.'
```

New behavior:
```
In [1]: from psychopy.sound import Sound
pygame 1.9.4
Hello from the pygame community. https://www.pygame.org/contribute.html

In [2]: input('foo> ')
foo> bar.
Out[2]: 'bar.'
```

psychopy/sound/backend_sounddevice.py

@@ -18,6 +18,7 @@
 
 try:
     import sounddevice as sd
+    import readline  # Work around GH-2230.
 except Exception:
     raise DependencyError("sounddevice not working")
 try: