Add newline to StringIO

[matthewhegarty]

This is a fix for #517. Adding the newline kwarg to StringIO handles interpreting the LF char.

https://docs.python.org/3/library/functions.html#open-newline-parameter

[codecov[bot]]

Codecov Report

Merging #518 (12aace0) into master (d9a4a97) will increase coverage by 0.01%. The diff coverage is 100.00%.

:exclamation: Current head 12aace0 differs from pull request most recent head 10bd273. Consider uploading reports for the commit 10bd273 to get more accurate results

@@            Coverage Diff             @@
##           master     #518      +/-   ##
==========================================
+ Coverage   90.82%   90.84%   +0.01%     
==========================================
  Files          28       28              
  Lines        2660     2664       +4     
==========================================
+ Hits         2416     2420       +4     
  Misses        244      244              

Impacted Files	Coverage Δ
src/tablib/utils.py	100.00% <100.00%> (ø)
tests/test_tablib.py	98.62% <100.00%> (+<0.01%)	:arrow_up:

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[claudep]

Thanks! May I ask you to also add a line in HISTORY.md?

[matthewhegarty]

Have updated HISTORY as requested.