Add listener.ssl_certificate_id support to AWS ELB

[jpadvo]

This hopefully will tick off ELB > SSL Configuration for issue 28. Relies on pull request 78 for mitchellh/goamz.

[jpadvo]

The reason for the build failure may be that I added a test with a placeholder value for an SSL certificate id - your test account would need an SSL certificate, and the id in the test would need to be updated.

[pearkes]

Hm, so, I'd say if the tests are that dependent on having an SSL cert on your account we should do what we do for other unique things, which is set an environment variable (AWS_SSL_CERTIFICATE_ID=foobar) and only have that test run if that var is set. You can see how we do that here and here. Just make a specific precheck for the SSL test that checks for that env var. We can assume we'll only occasionally run this test, but that's ok! Can you also rebase against master and fix up these conflicts?

Thanks for the contribution! SSL for ELB is a big win.