Add jshint configuration.

Enable laxcomma to support the style of using single var keyword for all
require statements.

Fix a leaked global variable in test/server.test.js.

/to: @ritch @raymondfeng please review
/cc: @Schoonology

See also [Code Style Guide](https://strongloop.atlassian.net/wiki/display/SL/Code+Style+Guide) on our wiki.