Merge branch 'hotfix/0.0.6'
Added spec
clarified some spec wording
Updated README with return values
Merge branch 'feature/ensure_returns' into develop
Updated specs for re-memorize error
Factis::Memory.memorize raises on known fact
Added the ability to overwrite a fact
Described the new behavior in README
Merge branch 'feature/double_memorization_error' into develop