extract init_all from create_all in worker
add allow_lossy option to allow lossy workers and optimizations, needed for #65
use init to initialize jpegrecompress worker only if allow_lossy
conform indent in jpegrecompress worker
rename QUALITY_OPTIONS to QUALITY_NAMES in jpegrecompress worker
remove lossless quality in jpegrecompress worker
build quaility names description from QUALITY_NAMES in jpegrecompress worker
add handling of lossy only workers to "optimizes at least one test image" spec
add entries to changelog, readme and gemspec about jpeg-recompress and optional lossy compression, resolves #65
no skipping missing workers in optimizes at least one test image spec
compact creation of optimizes image specs
specs for both lossless and lossy optimizations
extract Worker class methods to module Worker::ClassMethods
move all requires in image_optim to top