Proving that a "member" can create a valid image post w/o caption.

RSpec: 129 examples, 0 failures
Script: 0 tests: 0 failures, 0 errors, 0 pending, 0 omitted
RuboCop: 45 files inspected, no offenses detected
RuboCop global overrides in `.rubocop.yml`: 2
RuboCop local overrides in our source/spec files: 5