Support encoding detection

Some go servers mistakenly generate sgf files without correct CA
properties. Use chardet to detect first 300 bytes.

Signed-off-by: Carton He <cartonhe@gmail.com>

setup.py

@@ -47,6 +47,7 @@ setup(
         "urllib3",
         "pygame;platform_system=='Darwin'",  # some mac versions need this for kivy
         "screeninfo;platform_system!='Darwin'",  # for screen resolution, has problems on macos
+        "chardet",  # for automatic encoding detection
     ],
     dependency_links=["https://kivy.org/downloads/simple/"],
     python_requires=">=3.6, <4",