This is a bigger commit than I'd like. The test data files have been moved to the testdata directory, which will late contain the larger files for performance testing. The paths in ds_test have all been updated both for the new directory and to use relative paths. I've added test for each of the valid a and q switches (using a fastq example file). I've added try ... finally to the file opening code to ensure the file is always closed. I've removed the U mode from the file read in line with the deprication warning.