V4 -- remove asset size warning on dev builds

[sthzg]

New webpack versions introduce a warning when chunk sizes are above a threshold. As during dev the non-optimized bundles are served a bunch of warnings appear both in the terminal and the web dev console. Should be fixed by configuring that warning to only appear in dist builds.

Update: background https://medium.com/webpack/webpack-performance-budgets-13d4880fbf6d#.jq5mf9hlb

Configurable with

// in Dev.js, Test.js
performance: {
  hints: false
}