Extend cljam.core reader/writer functions.

[alumi]

Current cljam.core supports only SAM, BAM and FASTA files.

This PR adds other readers/writers to cljam.core.

[codecov]

Codecov Report

Merging #75 into master will increase coverage by 0.11%.
The diff coverage is 96.29%.

@@            Coverage Diff             @@
##           master      #75      +/-   ##
==========================================
+ Coverage   82.92%   83.04%   +0.11%     
==========================================
  Files          59       59              
  Lines        3795     3833      +38     
  Branches      409      409              
==========================================
+ Hits         3147     3183      +36     
- Misses        239      241       +2     
  Partials      409      409

Impacted Files	Coverage Δ
src/cljam/core.clj	96.66% <96.29%> (+5.75%)	⬆️
src/cljam/sorter.clj	76.72% <0%> (-2.59%)	⬇️
src/cljam/convert.clj	61.29% <0%> (+3.22%)	⬆️

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[totakke]

Good job. Thanks.

[alumi]

Thank you for the reviewing!