Use bgzip as default for writing .gz files

[alumi]

Fixes #251

This PR changes the behavior of cljam.util/compressor-output-stream.
It now returns BGZFOutputStream instead of GzipCompressorOutputStream for files with .gz extension.
Since BGZIP is just a special case of GZIP, existing codes using cljam.util/compressor-output-stream with .gz should still work.
To get GzipCompressorOutputStream, we can use the 2nd argument or .gzip extension.

This PR also includes

• Update log4j to 2.17.0
• Some minor fixes suggested by linters

[codecov]

Codecov Report

Merging #253 (ebac5b4) into master (7e7ba7f) will decrease coverage by 0.10%.
The diff coverage is 53.84%.

@@            Coverage Diff             @@
##           master     #253      +/-   ##
==========================================
- Coverage   88.70%   88.60%   -0.11%     
==========================================
  Files          76       76              
  Lines        6305     6308       +3     
  Branches      438      441       +3     
==========================================
- Hits         5593     5589       -4     
- Misses        274      278       +4     
- Partials      438      441       +3     

Impacted Files	Coverage Δ
src/cljam/util.clj	80.95% <53.84%> (-10.58%)	⬇️
src/cljam/algo/sorter.clj	92.15% <0.00%> (-0.08%)	⬇️

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[r6eve]

LGTM

[niyarin]

LGTM 👍

[alumi]

@r6eve @niyarin Thank you for reviewing! 👍