Use native golang caching

Merge pull request #19 from VoycerAG/use-stdlib-caching

Refactor caching to use stdlib

Improved logging and write security

Merge pull request #16 from VoycerAG/hardening_performance

Write concern for new images

Add experimental face detection

Merge pull request #13 from VoycerAG/smartcrop

Add optional face recognition

New API to support extensions

Merge pull request #10 from VoycerAG/next

Recode of image server

Improved gorelic monitoring

Merge pull request #8 from VoycerAG/improved_monitoring

Improved monitoring

Inherit metadata for thumbnails

Merge pull request #6 from VoycerAG/inherit_metadata

Enable inheritance of metadata.