Add a README with version and ipython-specific changes info.

IPython/frontend/html/notebook/static/codemirror/README-IPython.rst

@@ -0,0 +1,33 b''
+=======================
+ CodeMirror in IPython
+=======================
+
+We carry a mostly unmodified copy of CodeMirror.  The current version we use
+is (*please update this information when updating versions*)::
+
+  CodeMirror 2.15
+
+The only changes we've applied so far are these::
+
+    diff --git a/IPython/frontend/html/notebook/static/codemirror/mode/python/python.js b/IPython/frontend/html/notebook/static/codemirror/mode/python/python.js
+    index ca94e7a..fc9a503 100644
+    --- a/IPython/frontend/html/notebook/static/codemirror/mode/python/python.js
+    +++ b/IPython/frontend/html/notebook/static/codemirror/mode/python/python.js
+    @@ -5,7 +5,11 @@ CodeMirror.defineMode("python", function(conf, parserConf) {
+	     return new RegExp("^((" + words.join(")|(") + "))\\b");
+	 }
+
+    -    var singleOperators = new RegExp("^[\\+\\-\\*/%&|\\^~<>!]");
+    +    // IPython-specific changes: add '?' as recognized character.
+    +    //var singleOperators = new RegExp("^[\\+\\-\\*/%&|\\^~<>!]");
+    +    var singleOperators = new RegExp("^[\\+\\-\\*/%&|\\^~<>!\\?]");
+    +    // End IPython changes.
+    +    
+	 var singleDelimiters = new RegExp('^[\\(\\)\\[\\]\\{\\}@,:`=;\\.]');
+	 var doubleOperators = new RegExp("^((==)|(!=)|(<=)|(>=)|(<>)|(<<)|(>>)|(//)|(\\*\\*))");
+	 var doubleDelimiters = new RegExp("^((\\+=)|(\\-=)|(\\*=)|(%=)|(/=)|(&=)|(\\|=)|(\\^=))");
+
+
+In practice it's just a one-line change, adding `\\?` to singleOperators,
+surrounded by a comment.  We'll turn this into a proper patchset if it ever
+gets more complicated than this, but for now this note should be enough.