2.7

What's Changed

• Move null check into AbstractConstraintAdapter by @SentryMan in #272
• add groups to valid by @SentryMan in #274
• Change andThen() to continue false when first validator is false by @rbygrave in #275
• Add support for sharing instances of NotNull NotBlank adapters by @rbygrave in #277
• Refactor CoreAdapterBuilder cache use by @rbygrave in #276
• Tidy Validation Adapter by @SentryMan in #278

Full Changelog: 2.6...2.7