Bug fix release.
- presignedPostPolicy now to include port in URL string if the port is neither 80 or 443. (#450)
- presignedPostPolicy sets default expiration to 7 days. (#451)
- Resource leaks fixed, registered callbacks should be called. (#454)
- presignedGet now supports overriding response headers. (#453)
- statObject Etag is optional fix a crash. (#455)
- Other misc documentation updates.