Fix issue #39 - zcat < file

[peterk87]

See issue #39

To test:

# install bio_hansel
pip install git+https://github.com/phac-nml/bio_hansel.git@fix-39-zcat-mac-osx
# get test data
wget ftp://ftp.sra.ebi.ac.uk/vol1/fastq/SRR120/002/SRR1203042/SRR1203042_1.fastq.gz
# run bio_hansel on test data
hansel SRR1203042_1.fastq.gz

should produce output similar to:

sample  scheme  scheme_version  subtype all_subtypes    tiles_matching_subtype  are_subtypes_consistent inconsistent_subtypes   n_tiles_matching_all    n_tiles_matching_all_expected      n_tiles_matching_positive       n_tiles_matching_positive_expected      n_tiles_matching_subtype        n_tiles_matching_subtype_expected  file_path       avg_tile_coverage       qc_status       qc_message
SRR1203042      heidelberg      0.5.0   2.2.1.1.2       1; 2.2.1.1.2    2592097-2.2.1.1.2       False   ['1', '2.2.1.1.2']      149     202     3       18['SRR1203042_1.fastq.gz']        14.169934640522875      FAIL    "FAIL: Missing Tiles Error 1: 27.23% missing tiles; more than 5.00% missing tiles threshold. Low coverage depth (14.4 < 20.0 expected); you may need more WGS data. | FAIL: Mixed Sample Error 2: Mixed subtypes found: ""1; 2.2.1.1.2""."

specifically the subtype equal to 2.2.1.1.2 which indicates that the fastq.gz parsing is working correctly under OSX.

This fix works on Mac OSX 10.13.5 Beta and 10.12.6