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/)
Correct phpdoc for ResultSet::getResults
Merge pull request #435 from Topface/better-phpdoc

Correct phpdoc for ResultSet::getResults
Fix collision of Elastica\Type and Elastica\Filter\Type in \Elastica\Filter\Ids
Ensure Type() and Filter\Type() can be used together
Add explanation to testFilterTypeAndTypeCollision()
Merge pull request #438 from mrzard/fix-filter-type-collision

Fix collision of Elastica\Type and Elastica\Filter\Type in \Elastica\Filter\Ids
Add a getQuery getter to FilteredQuery

The `getFilter` method was already here, but there was no way to get the Query object back for manipulations.
Remove extra blank line
Add test for FilteredQuery getters and complete the changes file
Merge pull request #442 from damienalexandre/patch-1

Add a getQuery getter to FilteredQuery
Merge remote-tracking branch 'upstream/master' into patch-1
Add testGetDocumentWithFieldsSelection test case
Merge pull request #411 from loris/patch-1

Add support for fields parameter in get operation
Add optimize to status test to make sure all indices are added
Support for "proxy" param for http connections

If proxy passed (empty or actual proxy string), it will
override proxy configuration from environment.
Merge pull request #430 from Topface/http-proxy

Support for "proxy" param for http connections
Implement \ArrayAccess on Elastica\ResultSet

To ease customisation and access to the Results,
we can now get the results manualy.

Not sure about offsetUnset, maybe it should just throw an Exception
Add documentation and tests
Release v0.90.2.0