DataLoader to check for batch size of 1 an ignore

[sreeshnair]

A batch of size 1 should not be included in the DataLoader. We want to have the DataLoader handle this (but still keep batches of size > 1) and then remove the logic in learner.py that handles skipping batches of size 1.

DataLoader to check for batch size of 1 an ignore

Remove logic to check for batch size of 1 from learner.py

https://shoprunner.atlassian.net/browse/DS-2406

Pull Request Checklist

• [x] All tests in the tests folder pass with a local build
• [x] Pull request includes a description of why we are doing this
• [x] Init files import new capabilities to appropriate level of package (if applicable)
• [x] CHANGELOG has been updated
• [x] Version in _version.py has been updated
• [x] README has been updated (if applicable)
• [x] requirements.txt and requirements-dev.txt have been recompiled if requirements in setup.py or requirements-dev.in changed.