TypeScript compiler will now build to ES2015 code and modules. Babili is used to minify ES2015
code, providing an initial optimization that we couldn't previously get just from Uglify. Uses
Babel to convert ES2015 to UMD/ES5 code, and Uglify to minimize the output.
This change installs HttpModule with ServerModule, and overrides bindings to
service Http requests made from the server with the 'xhr2' NPM package.
Outgoing requests are wrapped in a Zone macro-task, so they will be tracked
within the Angular zone and cause the isStable API to show 'false' until they
return. This is essential for Universal support of server-side HTTP.
