v2.0.0-alpha.1

The first alpha release in preparation of version 2 of the validator. In this release:

• The result of ->validate() now returns a validation result, on which you can call isValid, isNotValid and getMessages.
• PHP7 compatibility
• Add LessThan and GreaterThan rule

Note that this is an alpha release of version 2. For version two we have some other features planned, that might break backwards compatibility over the v2-alpa's up to version 2.