Merge branch 'hotfix/v0.5.1'
New tests for UriValidator and fixing IDE warnings
Fixing UriValidator to pass old and new tests
Fixing phpdoc for DateTimeValidator
Tests for null arguments in constructor
Fixing IDE warnings
Bumping version to 0.5.2
Updating guidelines for contributing with code.
Merge branch 'hotfix/v0.5.2' into develop