refactor file hash computation into its own function
refactor opening of signed JAR file into its own function
remove last link in promise chain attached to task
remove unnecessary 'self' reference
use 'cleanup' reference consistently
use fullPackagePath consistently
define variables as locally and lazily as possible
factor out requestChannel retrieval into its own function
factor out more requestChannel configuration into the _getRequestChannel function
factor out statusCode check to _getPackage function
factor out HTTP response status check to _getPackage function
factor out reading of package to its own function
declare lastProgressTime in the correct place; manifest -> newManifest to clarify meaning; minor formatting changes