* Update CHANGELOG.md

* Dark-launch new semver matching logic for yarn

Running upx on go binaries reduces binary size ~ from 7MB -> 1.5MB

* Deprecate iojs

* Add logic for fetching S3 objects

* Add logic for parsing s3 paths

* Stub out go binary build and tests

* Clean up script metrics and logging

* Log build scripts out before they are run

* Fix tests and broken implementation

* Separate prebuild step in log output

* Add metadata logging when the build fails

* Add temporary bright warning about breaking change

* Run the build script by default

This removes the opt-in behavior and defaults users into running
the "build" script by default. Users that were opted-in will see
no change

Fixes #632

* Improve changelog entry for v119

* Fix yarn run error when script is empty string

Currently the `build` step gets jumbled up with the `npm install` step. Let's cleanly separate the two

This generates random uuids for both each build run, and the app itself. It then propagates the app uuid through each subsequent build by serializing it into the cache.

This isn't completely ideal because PR apps will each get their own app uuid, but it should still allow us to do better analysis on our log data than we currently can.

Questions like "How many apps failed yesterday?" vs "How many builds failed yesterday"?

The build uuid helps make sure that we aren't ever double counting events somehow.

Adds a cross-platform compatible command to generate `uuid`s

Currently we're tracking the time spent in parts of the build process, like installing `node_modules` or running the build command, but we're not tracking how long the whole build takes. Let's fix that.

Also removes a stray `new-build-script-opt-in` call that wasn't doing anything

This makes sure that even in the case where a `heroku-postbuild` script is completely empty, it will still be preferred over the `build` script.

* Add warning for the upcoming run build change

Make sure that failing builds in CI actually fail

Automatically make the metadata from the previous run available by copying it at the start of the build. This will be used to provide better failure messages.

Bring in the new build metadata module and add calls to store this info in the cache