message: doc(README): Update description
diff: @@ -3,10 +3,18 @@ itk.js
  [![CircleCI](https://img.shields.io/circleci/project/github/InsightSoftwareConsortium/itk-js/master.svg)](https://circleci.com/gh/InsightSoftwareConsortium/itk-js)
  -Provides general scientific image, mesh, and point set IO capability and bridges
  -[ITK](https://itk.org) code running in an
  -[asm.js](http://asmjs.org/) or [WebAssembly](http://webassembly.org/)
  -runtime environment.
  +*itk.js* combines [Emscripten](http://emscripten.org/) and
  +[ITK](https://www.itk.org/) to enable high-performance spatial analysis in a
  +JavaScript runtime environment.
  +
  +The project provides tools to a) build C/C++ code to JavaScript
  +([asm.js](http://asmjs.org/)) and [WebAssembly](http://webassembly.org/), b)
  +bridge local filesystems, native JavaScript data structures, and traditional
  +file formats, c) transfer data efficiently in and out of the Emscripten
  +runtime, and d) asynchronously execute processing pipelines in a background
  +thread. *itk.js* can be used to execute [ITK](https://www.itk.org/),
  +[VTK](https://www.vtk.org/) or arbitrary C++ codes in the browser or on a
  +workstation / server with Node.js.
  For more information, please see [the project
  documentation](https://insightsoftwareconsortium.github.io/itk-js/).
  