Complete rewrite.
Split out enable option to two options.
Add object prefix setting.
Confirmation message for saving settings.
Closes #5: Remove local file after uploading to S3
Fixes #17: Mismatch between local and S3 dir paths
Closes #4: Interoperability with WP Retina 2x plugin
Added force SSL option. Closes #19
Support any HiDPI plugin.
Support S3 object versioning. Closes #3
Fix undefined index bug.
Update version and release notes.