Add model for recording transaction archives.
Outline of archival functions.
Utility class for uploading to S3 buckets.
Alter TransactionArchive statuses to better match archive workflow.
Implement uploading archives to S3.
Require boto and moto (moto mocks boto).
Skeleton for s3util tests.
Refactor s3util Bucket and BucketConfig to give them a more consistent API.
Tests for s3utils.BucketConfig.
Merge branch 'feature/issue-1060-update-statement-generation' into feature/issue-1061-update-billing-statement-pdf-static-content-and-styling
Add tests for buckets and multipart uploads.
Merge branch 'develop' into feature/issue-868-archive-transactions
Use a newer version of six in Travis.
Merge branch 'develop' into feature/issue-868-archive-transactions

Conflicts:
	go/billing/tasks.py
Remove custom six install since it doesn't seem to help with Travis builds.
Try depending on a recent version of six directly.
Merge branch 'develop' into feature/issue-1061-update-billing-statement-pdf-static-content-and-styling
Remove direct dependency on six since that doesn't help either.
Add pip freeze to before build scripts so we can see package versions succinctly when trying to debug obscure build failures.
Merge branch 'feature/issue-1062-relax-requests-version' into feature/issue-868-archive-transactions