Add support for grouping result using a function

Add functionality that checks whether the result data in
ResponseParser\Component\Grouping contain groups created by
solr parameter `group.func` (an arbitrary Solr-supported
function).

When such field is found, apply the same parsing logic
which is usually used for field-grouping, in order to ensure
the function-grouping is recognized and added to the FieldGroup
result object.

Fix fenced block start.

Do not parse collation array for Solr 5+; values are already in name/value pairs. Change unit test to match the collation data structure returned by Solr.

Do not parse collation array for Solr 5+; values are already in name/value pairs. Change unit test to match the collation data structure returned by Solr.

fix sample-code in Plugin System section

Merging develop to master for new release

Fix readthedocs domain

Update coveralls settings

Actually use ClientInterface

corrects php docblock in result-of-a-select-query

fix typo on docs index.md

It's a pretty glaring error on the main page (and thus on Google results).

Stats percentiles

Chcek existance of stats value before returning.

Added option to add multiple boostqueries to dismax parser

Fixed some types.

added support for replicas in distributed search

Added unit tests for QueryType\Select\Query\Component\DisMax::addBoostQuery, addBoostQueries.

addition of the replicas property so the request builder can use both shards and replicas in the shard param

Allow symfony/class-loader 3.0 to be installed