Patches
- Read compiler.context instead of this.context: #3839
- Upgrade react-hot-loader to beta 23: #3843
- [SSR] Use relative paths in dynamic import output code: #3844
- Merge master into canary: #3846
- prefetch is a production only feature: #3851
- Fix w3c warnings: #3572
- Remove special error script handling: #3849