Merge branch 'master' into handle-categories-in-site-config-defaults
Set categor[y|ies] on post if they appear in site frontmatter defaults
Update `Utils#pluralized_array_from_hash` and `Utils#value_from_singular_key` per suggestion from @parkr

Switched to using the `#tap` method for more concise code. Also returning the value from
`value_from_singular_key` instead of returning an array wrapped presentation of the value.
This allows for a one-liner in `pluralized_array_from_hash`.
Merge pull request #2373 from tschmidt/handle-categories-in-site-config-defaults