Elastica\Result should have hasFields() method

To make it consistent with Elastica\Document
Add missing hasParam() method

However in the long run it might make more sense to extend Param class
Added tests for hasFields()
Fix failing test in ResultTest
Merge branch 'master' of https://github.com/ruflin/Elastica
Merge pull request #513 from MrHash/master

Elastica\Result should have hasFields() method