[MODEL] Added, that options are passed to `SearchRequest` in `search`

Closes #3
[MODEL] Added missing test for Response::Records#ids
[MODEL] Added the ability to pass a custom index name to .create_index!, .delete_index! and .refresh_index!
[MODEL] Added the ability to import records into a different index/type

    Article.import index: 'my-new-index', type: 'my-other-type'
[RAILS] Added a the file with Rake tasks for importing the model(s)

Add this e.g. into the `lib/tasks/elasticsearch.rake` file in your Rails application:

    require 'elasticsearch/rails/tasks/import'

Run this command inside your application folder to display usage instructions:

    bundle exec rake -D elasticsearch
[RAILS] Added information about the provided Rake tasks into the README
[MODEL] [TEST] Removed hardcoded port 9250 and used ENV['TEST_CLUSTER_PORT'] in test cluster initialization
[RAILS] Updated the dependencies for `elasticsearch-rails`

* Load -model from disk if available
* Remove coveralls (breaks with Rails, useless anyway)
[RAILS] Added test helper for `elasticsearch-rails`
[RAILS] Added ActiveSupport instrumentation integration

Require the component in your `application.rb` file:

    require 'elasticsearch/rails/instrumentation'

You should see an output like this in your application log in development environment:

    Article Search (321.3ms) { index: "articles", type: "article", body: { query: ... } }

Also, the total duration of the request to Elasticsearch is displayed in the Rails request breakdown:

    Completed 200 OK in 615ms (Views: 230.9ms | ActiveRecord: 0.0ms | Elasticsearch: 321.3ms)

A special component for the Lograge logger implementation is provided as well.

See:

* http://edgeguides.rubyonrails.org/active_support_instrumentation.html
* http://api.rubyonrails.org/classes/ActiveSupport/Notifications.html
* https://github.com/roidrage/lograge
[TEST] Execute tests in the `test:all` Rake task manually, to prevent dependency loading errors

Should prevent errors like:

    .../elasticsearch-rails/elasticsearch-rails/test/test_helper.rb:21:in `require': cannot load such file -- rails/version (LoadError)
      from .../elasticsearch-rails/elasticsearch-rails/test/test_helper.rb:21:in `<top (required)>'

See:

* https://api.travis-ci.org/jobs/18002966/log.txt?deansi=true
* http://build.elasticsearch.com/view/Clients/job/es-rails_core/ES_V=1.x_nightly,GEMFILE=4.0.gemfile,RUBY_V=2.0.0-p247,label=not-es/lastCompletedBuild/consoleText