Add failing syntax error + transform test

Ref 9fe46d5#commitcomment-28273437

Author: goto-bus-stop

test/files/syntax_error.js

@@ -0,0 +1,2 @@
+const a = require('a');
+const a = 0;

test/syntax.js

@@ -0,0 +1,19 @@
+var mdeps = require('../');
+var test = require('tap').test;
+var JSONStream = require('JSONStream');
+var packer = require('browser-pack');
+var through = require('through2');
+var path = require('path');
+
+test('syntax error', function (t) {
+    t.plan(1);
+    // ensure transformDeps functionality does not break when parse errors happen
+    // see https://github.com/browserify/module-deps/commit/9fe46d5#commitcomment-28273437
+    var p = mdeps({
+        transform: function () { return through(); }
+    });
+    p.on('error', function (err) {
+        t.ok(err);
+    });
+    p.end(path.join(__dirname, '/files/syntax_error.js'));
+});