Refactor core action to return a parser instance based on the response body.

Remove valid_content? requirement and after_initialize support in parser

Add Response class to core to provide consistent interface for Conduit::Core::Action.

Style cleanup; adding .rubocop.yml

Remove Parser#raw_content

Replace Conduit::Core::Response with Conduit::Response; rescue Excon::Errors::Timeout in Connection.
Merge pull request #86 from conduit/ATOM-1536_conduit_refactor

Refactor core action to return a parser instance based on the response body