def connection_adapter(custom_adapter = nil, options = nil)
      if custom_adapter.nil?
        default_options[:connection_adapter]
      else
        default_options[:connection_adapter] = custom_adapter
        default_options[:connection_adapter_options] = options
      end
    end
def connection_adapter(custom_adapter = nil, options = nil)
      if custom_adapter.nil?
        default_options[:connection_adapter]
      else
        default_options[:connection_adapter] = custom_adapter
        default_options[:connection_adapter_options] = options
      end
    end
Allows setting a custom connection_adapter for the http connections

 @example
   class Foo
     include HTTParty
     connection_adapter Proc.new {|uri, options| ... }
   end

 @example provide optional configuration for your connection_adapter
   class Foo
     include HTTParty
     connection_adapter Proc.new {|uri, options| ... }, {foo: :bar}
   end

 @see HTTParty::ConnectionAdapter