Initial changes to eventually support asynchronous optimization.
Page bundles are now built asynchronously.
Additional changes to support async and sync optimization
Additional changes to support async optimization
Removed unused argument
Switched to resolving with context instead of writer output
Bug fix for renderToStringAsync
Improved jsdom test harness
Switched to using promises and improved jsdom test harness
Added support for putting a promise for an optimized page
Additional refactoring to convert the RaptorJS optimizer to async