remove doublequotes from convert arguments
change buildCommandString() to return array instead of string
remove tmp download and add stream resizing
update tests
refactor generateCacheFilename()
Merge branch 'feature/pipe_to_magick' into develop
bump version to 0.4.0
add config options for cache-control max-age and expires header
add better error handling and remote content checks
add check for status 404 to validateRemoteSource()
update tests for validateRemoteSource()