Always load source files in binary mode.

Source files can be in any coding system, provided Python can
read a coding: line at the beginning of the file. So source files
should be loaded in binary format and decoded according to that
line, not assumed to be in the default coding system.

Fixes #398.

jedi/_compatibility.py

@@ -31,9 +31,7 @@ def find_module_py33(string, path=None):
             module_file = None
         else:
             module_path = loader.get_filename(string)
-            module_ext = os.path.splitext(module_path)[1]
-            mode = 'rb' if module_ext in ['.pyc', '.so', '.pyd'] else 'r'
-            module_file = open(module_path, mode)
+            module_file = open(module_path, 'rb')
     except AttributeError:
         # ExtensionLoader has not attribute get_filename, instead it has a
         # path attribute that we can use to retrieve the module path