Verify downloaded test runner zip file 812 (#4193)

* if download has checksum use it to verify downloaded file

* check only filesize if no checksum available

* add download tests

* move checksum into util for reuse, be explicit

* add comments explaining headers used to verify checksum

* move hasha to dev dependency

* remove unnecessary function

* do not use deprecated Promise.join with spread

* fix promise join callback

* linting

scripts/binary/upload-unique-binary.coffee

@@ -96,7 +96,7 @@ setChecksum = (filename, key) =>
   la(check.unemptyString(filename), 'expected filename', filename)
   la(check.unemptyString(key), 'expected uploaded S3 key', key)
 
-  checksum = hasha.fromFileSync(filename)
+  checksum = hasha.fromFileSync(filename, { algorithm: 'sha512' })
   size = fs.statSync(filename).size
   console.log('SHA256 checksum %s', checksum)
   console.log('size', size)