5.1.0

Features

• Added spanish translation thanks to @Dionakra (#401)
• New test: <select required> should start with an empty value option (#406)
• Updated test: take tabindex negative values into account (#360)
• Dropped :blank and :-moz-only-whitespace to allow file size improvements (#365)

Chore

• Drop package-lock.json to only use Yarn
• Update Yarn & Bundler dependencies