Summary:
There are two fs steps and it wasn't clear why. This now puts the right label:
```
[9:38:25 PM] <START> Building in-memory fs for JavaScript
[9:38:27 PM] <END> Building in-memory fs for JavaScript (2030ms)
[9:38:27 PM] <START> Building in-memory fs for Assets
[9:38:27 PM] <END> Building in-memory fs for Assets (615ms)
```
Summary:
@public
Fixes#773, #1055
The resolver was getting a bit unwieldy because a lot has changed since the initial writing (porting node-haste).
This also splits up a large complex file into the following:
* Makes use of classes: Module, AssetModule, Package, and AssetModule_DEPRECATED (`image!` modules)
* DependencyGraph is lazy for everything that isn't haste modules and packages (need to read ahead of time)
* Lazy makes it fast, easier to reason about, and easier to add new loaders
* Has a centralized filesystem wrapper: fast-fs (ffs)
* ffs is async and lazy for any read operation and sync for directory/file lookup which makes it fast
* we can easily drop in different adapters for ffs to be able to build up the tree: watchman, git ls-files, etc
* use es6 for classes and easier to read promise-based code
Follow up diffs will include:
* Using new types (Module, AssetModule etc) in the rest of the codebase (currently we convert to plain object which is a bit of a hack)
* using watchman to build up the fs
* some caching at the object creation level (we are recreating Modules and Packages many times, we can cache them)
* A plugin system for loaders (e.g. @tadeuzagallo wants to add a native module loader)
Test Plan:
* ./runJestTests.sh react-packager
* ./runJestTests.sh PackagerIntegration
* Export open source and run the e2e test
* reset cache
* ./fbrnios.sh run and click around
