Build not saved to S3

[Deleted user]

After merging this PR #5, builds appear to succeed again in the console:

thaumaturgy build foo:latest
Invoking Thaumaturgy Lambda in AWS with packagesfoo:latest.
Build completed successfully.
Results at: s3://my-bucket/thaumaturgy.zip

However the s3 bucket is still empty. Thaumaturgy is either failing to create the binary or failing to save it to s3.