AWS Integration Improvements

Ensures that AWS Daily Limits are followed even if no auto batching is
enabled
Added a check for batch size

Improvements to previous commit
Ensures no sending when batch_size is 0

Refer to issue highlighted:
https://github.com/justingit/dada-mail/pull/442#issuecomment-44816756
Fixes bugs introduced in last commit
Batch Size Detection Improvements
Revert "Fixes bugs introduced in last commit"

This reverts commit 8f50e03a1e9051432c79ff4e9d9d60d57f1cd4ad.
Revert "Ensures no sending when batch_size is 0"

This reverts commit 5b0f65859a4d49b6205a1761560146f117ab33cd.
Merge branch 'Yunheng-master' into ses_fixes_06_03_14