Ensure that color is in use as a link background or border color.

Closes #65.
Don't consider blank aliases in uniqueness validations. Closes #66.
Merge pull request #68 from msrose/feature/expand-color-scope

Ensure that color is in use as a link background or border color.
Merge pull request #67 from msrose/feature/allow-blank-alias

Don't consider blank aliases in uniqueness validations. Closes #66.
Merge branch 'master' into stable