examples/snippets: fix error in case .pyc files of snippets are present. Fixes #35

The code assumed that module.__file__ points to the source, but it
points to the .pyc file in case it exists. Use inspect.getsource()
instead.

examples/cairo_snippets/snippets/__init__.py

@@ -1,4 +1,5 @@
 import os
+import inspect
 import importlib
 
 
@@ -30,7 +31,9 @@ def get_snippets():
         s.name = name
         mod = importlib.import_module("." + name, __package__)
         s.draw_func = getattr(mod, "draw")
-        with open(mod.__file__, "rb") as h:
-            s.code = h.read().decode("utf-8")
+        code = inspect.getsource(mod)
+        if isinstance(code, bytes):
+            code = code.decode("utf-8")
+        s.code = code
         snippets[s.name] = s
     return snippets