Allow new aws api-gateway integration types
Allow new aws api-gateway integration types

The added types are 'AWS_PROXY' for integrating with lambdas and
'HTTP_PROXY' for integrating via http.

See http://docs.aws.amazon.com/apigateway/api-reference/resource/integration/

ClementCunin/terraform-provider-aws,nbaztec/terraform-provider-aws,ashinohara/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,terraform-providers/terraform-provider-aws,ClementCunin/terraform-provider-aws,Ninir/terraform-provider-aws,ashinohara/terraform-provider-aws,terraform-providers/terraform-provider-aws,Ninir/terraform-provider-aws,ClementCunin/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,Ninir/terraform-provider-aws,kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws,nbaztec/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,nbaztec/terraform-provider-aws,ashinohara/terraform-provider-aws,kjmkznr/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,nbaztec/terraform-provider-aws,ashinohara/terraform-provider-aws,terraform-providers/terraform-provider-aws,Ninir/terraform-provider-aws,ClementCunin/terraform-provider-aws