Fix acceptance tests for filestore, run on travis

Code changes:  FileHandler deleteFile method
 -  fix use of converted bucket name (only first argument of getConvertedFolderKey is used)
 - call deleteDirectory on converted cache directory, to make deleteFile inverse of insertFile

FS-only changes:
 - use rimraf to delete directory recursively
 - use 'response' module to return HTTP "NoSuchKey" response for missing file, as on S3
 - copyFile calls success callback on completion, instead of immediately

Test changes:
 - updates to match above
 - run acceptance tests with forever on travis