Fix misuse of with-open

[athos]

The root cause of #35 seems to be the fact that even after adding the IReader protocol's own close method in 8519c72 instead of Closeable#close, some code has been using with-open to close the IReader implementation as before by mistake.

This PR fixes those misuses of with-open.

[codecov]

Codecov Report

Patch coverage: 90.90% and project coverage change: +0.04 🎉

Comparison is base (ef49810) 88.96% compared to head (094c782) 89.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #36      +/-   ##
==========================================
+ Coverage   88.96%   89.00%   +0.04%     
==========================================
  Files          13       13              
  Lines        1015     1019       +4     
  Branches       48       48              
==========================================
+ Hits          903      907       +4     
  Misses         64       64              
  Partials       48       48              

Impacted Files	Coverage Δ
src/pogonos/api.clj	84.81% <0.00%> (ø)
src/pogonos/core.cljc	85.57% <100.00%> (ø)
src/pogonos/reader.cljc	94.77% <100.00%> (+0.16%)	⬆️

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