Update test framework: fix run_tests.py to support all test files, add auto-import-check for test files

node_modules/tdigest/gruntfile.js

@@ -0,0 +1,16 @@
+module.exports = function(grunt) {
+    var pkg = grunt.file.readJSON('package.json');
+
+    grunt.initConfig({
+        pure_cjs: {
+            options: {
+                exports: 'tdigest',
+                comments: true
+            },
+            'dist/tdigest.js': 'tdigest.js'
+        }
+    });
+ 
+    grunt.task.loadNpmTasks('grunt-pure-cjs');
+    grunt.registerTask('dist', ['pure_cjs']);
+}