Update s3 high level commands to honor "--no-verify-ssl"

Fixes #696.

This fix is a little bit larger than probably expected because it solves the problem in the general case.  The top level global args are now resolved/subjected to additional processing before calling any command/subcommands.  This means that additional high level commands can just call `get_endpoint` with the parsed_args and they will get the verify ssl arg properly resolved already.

Also had to update the s3 commands to actually use the `verify_ssl` argument.  Tests added, and also manually verified:

```
$ aws s3 ls 2>&1 --no-verify-ssl --debug | grep verify_ssl
2014-03-10 14:28:40,647 - botocore.endpoint - DEBUG - Making request for Operation:ListBuckets (verify_ssl=False) with params: {'headers': {}, 'uri_params': {}, 'payload': <botocore.payload.XMLPayload object at 0x10c057250>}
```