README: `Case_Folding` are not maps

[mathiasbynens]

The generated READMEs contain things like:

// `Case_Folding`:

require('unicode-9.0.0/Case_Folding/C/code-points'); // lookup map from code point to code point
require('unicode-9.0.0/Case_Folding/C/code-points').get(codePoint);
require('unicode-9.0.0/Case_Folding/C/symbols'); // lookup map from symbol to symbol
require('unicode-9.0.0/Case_Folding/C/symbols').get(symbol);

However, the exported values are regular objects.