Prepare v1.2
Fix highlighter type values

As defined at the ElasticSearch highlighting reference, the valid values for the highlighter "type" field are "plain", "postings" and "fvh".
Update dist files.
Allow passing filter to HasChild and HasParent filter

Closes #59
Begin implementation of TopHitsAggregation
Fix indentation in TopHitsAggregation
Use proper mixin for TopHitsAggregation, also implement all supported fields for its AggregatorFactory
Add tests for TopHitsAggregation and fix errors found by tests