Add support for fields parameter in get operation

Update the getDocument method to return the `fields` field instead of `_source` if available.
Allows to get a document from ES and specify the fields you want (See fields section at http://www.elasticsearch.org/guide/reference/api/get/)
plugin geocluster-facet support added
Fix files bath to vagrant box #423
Add optimize to Alias test to make sure, alias is already propagated during travis test.
got rid of e-recoverable error
added comment and add few lines to changes.txt
changed a link to plugin
some cleanup
tests added
compatibility with 5.3 added
compatibility with 5.3 added
added plugin installation procedure to run_elasticsearch script
added plugin installation procedure to run_elasticsearch script
added plugin installation procedure to run_elasticsearch script
added plugin installation procedure to run_elasticsearch script
added plugin installation procedure to run_elasticsearch script
added plugin installation procedure to run_elasticsearch script
added plugin installation procedure to run_elasticsearch script
Merge pull request #421 from konstantinmopals/master

plugin geocluster-facet support added
Fix indentation in Elastica/Index