Added support for attaching auto scaling groups to target groups

[maf23]

This is in reference to #328
Unfortunately I will not have time to implement support for managing
the actual ALBs and all that is reated to them.

[lanej]

Because elb-test-fog is not a real object these tests fail horribly when performing live verification.

0] » FOG_MOCK=false be shindo tests/requests/auto_scaling/
[fog][WARNING] Setting default fog timeout to 2000 seconds

  AWS::AutoScaling | auto_scaling_tests (aws, auto_scaling)
    success
      #create_launch_configuration + has proper format
      #describe_launch_configurations + has proper format
      #describe_launch_configurations + has proper format
      #describe_launch_configurations + has proper format
      #create_auto_scaling_group + has proper format
      #attach_load_balancers - has proper format
      Provided Load Balancers may not be valid. Please ensure they exist and try again. (Fog::AWS::AutoScaling::ValidationError)
        ...
        /Users/jlane/.gem/ruby/2.3.3/gems/fog-xml-0.1.2/lib/fog/xml/sax_parser_connection.rb:35:in `request'
        /Users/jlane/.gem/ruby/2.3.3/gems/fog-xml-0.1.2/lib/fog/xml/connection.rb:7:in `request'
        /Users/jlane/p/fog-aws/lib/fog/aws/auto_scaling.rb:150:in `_request'
        /Users/jlane/p/fog-aws/lib/fog/aws/auto_scaling.rb:144:in `request'
        /Users/jlane/p/fog-aws/lib/fog/aws/requests/auto_scaling/attach_load_balancers.rb:27:in `attach_load_balancers'
        /Users/jlane/p/fog-aws/tests/requests/auto_scaling/auto_scaling_tests.rb:31:in `block (3 levels) in <top (required)>'
        tests/helpers/formats_helper.rb:92:in `block in formats'
        ...
        tests/helpers/formats_helper.rb:85:in `formats'
        /Users/jlane/p/fog-aws/tests/requests/auto_scaling/auto_scaling_tests.rb:30:in `block (2 levels) in <top (required)>'
        ...
        /Users/jlane/p/fog-aws/tests/requests/auto_scaling/auto_scaling_tests.rb:5:in `block in <top (required)>'
        ...
        /Users/jlane/p/fog-aws/tests/requests/auto_scaling/auto_scaling_tests.rb:1:in `<top (required)>'
        ...

There are similar errors for (at|de)tach_load_balancer{_target_groups} and (attach|detach)_instances. I'll wrap the offending calls in a mock only conditional after merge.

[lanej]

Thanks @maf23

[geemus]

Thanks!