Merge tag '0.58' into develop

Release 0.58
Support auth via AWS STS (Security Token)
Merge branch 'develop' of github.com:pfig/net-amazon-s3 into develop
Merging pull request #17 into feature/auth-token
Cosmetic, code style
Merge pull request #19 from pfig/feature/auth-token

Feature/auth token
Updated change log
Release 0.59