Treat double-width unicode characters

[hallazzang]

Describe the style change
Black currently does not handle double-width characters(i.e. CJK characters) different from single-width characters.
This leads black to make some lines too long to see in small(~88 characters width) window.
Please check the example below.

Examples in the current Black style
Consider this input:

foo = (
    ("aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb"),
    ("안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요"),
)

If I run black --diff main.py, then I get this result:

@@ -1,4 +1,15 @@
 foo = (
-    ("aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb", "aaaaabbbbb"),
+    (
+        "aaaaabbbbb",
+        "aaaaabbbbb",
+        "aaaaabbbbb",
+        "aaaaabbbbb",
+        "aaaaabbbbb",
+        "aaaaabbbbb",
+        "aaaaabbbbb",
+        "aaaaabbbbb",
+        "aaaaabbbbb",
+    ),
     ("안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요"),
 )

Desired style
I want black to style my code like this:

foo = (
    (
        "aaaaabbbbb",
        "aaaaabbbbb",
        "aaaaabbbbb",
        "aaaaabbbbb",
        "aaaaabbbbb",
        "aaaaabbbbb",
        "aaaaabbbbb",
        "aaaaabbbbb",
        "aaaaabbbbb",
    ),
    (
        "안녕하세요",
        "안녕하세요",
        "안녕하세요",
        "안녕하세요",
        "안녕하세요",
        "안녕하세요",
        "안녕하세요",
        "안녕하세요",
        "안녕하세요",
    ),
)

But black prevents it, rather does this:

@@ -8,17 +8,8 @@
         "aaaaabbbbb",
         "aaaaabbbbb",
         "aaaaabbbbb",
         "aaaaabbbbb",
     ),
-    (
-        "안녕하세요",
-        "안녕하세요",
-        "안녕하세요",
-        "안녕하세요",
-        "안녕하세요",
-        "안녕하세요",
-        "안녕하세요",
-        "안녕하세요",
-        "안녕하세요",
-    ),
+    ("안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요", "안녕하세요",),
 )

Additional context

$ black --version
black, version 19.10b0

[ichard26]

#1197 is a duplicate of this issue, but it has more context and discussion, so closing this in favour of that.