Made calls to 'blank?' and 'present?' easier to reason about

Made calls to 'blank?' and 'present?' easier to reason about by
changing code that did not need to be negative or double negative.
It's just easier to think about code that's written in a positive
way than negative code.

- Replaced 'unless blank?' with 'if present?'
- Replaced 'reject(&:blank?)' with 'select(&:present?)'
- Replaced '!blank?' with 'present?'
- Replaced '!include?' with 'exclude?'