test: introduce a test for process.versions output

make sure that process.versions contains an expected list of software to avoid
potential mistakes with refactoring.

PR-URL: #352
Reviewed-By: Rod Vagg <rod@vagg.org>

test/parallel/test-process-versions.js

@@ -0,0 +1,7 @@
+require('../common');
+var assert = require('assert');
+
+var expected_keys = ['ares', 'http_parser', 'modules', 'node',
+ 'openssl', 'uv', 'v8', 'zlib'];
+
+assert.deepEqual(Object.keys(process.versions).sort(), expected_keys);