Quote 'key.name' properly when used in URL path / query string.

Fixes #354.
Consistent dict literal formatting.

What did Emerson know, anyway?
Merge pull request #364 from tseaver/354-support_slash_in_key_names

Fix #354: support slash in key names
Spurious parameter.
More idiomatic use of '__iter__'.
Add 'Bucket.iterator' method.

Exposes additional paramters for narrowing / batching key search.

Fixes #26.
Capture 'prefixes' returned in iterator response.
Update TestStorageListFiles regression to use 'bucket.iterator'.

See: https://github.com/GoogleCloudPlatform/gcloud-python/pull/359#issuecomment-62643880