[DSL] Updated .gemspec and added Rake tasks
[DSL] Added the test helper
[DSL] Added the main DSL module
[DSL] Added the `BaseComponent` module for the DSL
[DSL] Added the initial Query implementation

* `Search` class with a `query` method
* Query classes for initial queries (match, range, term)
* Unit tests for all classes
* Basic integration test for the `match` query (skeleton for others)
[DSL] Added documentation for the current codebase
[DSL] Added the initial Filter implementation
[DSL] Added the `call` method to the BaseComponent
[DSL] Added BaseAggregationComponent with common logic for aggregation classes
[DSL] Added the Aggregation class to wrap aggregations in search definitions
[DSL] Added the "Terms" and "Range" aggregations
[DSL] Added the aggregations integration into the DSL

    response = client.search index: 'test', body: search {
      aggregation :tags do
        terms field: 'tags'
      end
    }.to_hash

    response['aggregations']['tags']['buckets'][0]['key']
    # => 'one'
[DSL] Added a sorting integration