Add .json extension again to match node default

Author: tmcw

Diff for: lib/input/dependency.js

@@ -33,7 +33,10 @@ function dependencyStream(indexes, options, callback) {
       return !!options.external || moduleFilters.internalOnly(id);
     },
     extensions: [].concat(options.extension || [])
-      .concat(['js', 'es6', 'jsx'])
+      // We don't document JSON files, but we do include them in this list,
+      // because browserify & node both support unnamed requires to .json
+      // files: `require('foo')` can require `foo.json` automatically.
+      .concat(['js', 'es6', 'jsx', 'json'])
       .map(function (ext) {
         return '.' + ext;
       }),