Remove .travis.yml (automated tests can't run w/o creds)

It'd be nice to later setup some public IAM creds for testing, but not worth
the effort right now.
Add `create-table` `:block?` option TODO
Housekeeping
Add `items-by-attrs` helper for bulk & query/scan result structuring
Implement `create-table` `:block?` option, add `block-while-table-status`