Fix stripping of enclosing parentheses

The current code strips _all_ surrounding parentheses, while only the
outermost should be stripped. This commit changes this.

Closes yskoht#91

keymapviz/__init__.py

@@ -84,7 +84,7 @@ def __parse_keymap_c(self):
             r'\s*(\w+(?<rec>\((?:[^()]|(?&rec))*\))*)\s*,?'
         )
         keymaps = keymap_regexp.findall(src)
-        keymaps = [_.lstrip('(').rstrip(')') for _ in keymaps]
+        keymaps = [re.sub(r"^\(?(.*)\)?$", r"\1", _) for _ in keymaps]
         keymaps = [[__[0] for __ in keycode_regexp.findall(_)] for _ in keymaps]
         return keymaps