Added Swedish Locale

[pierdet]

I saw that you were accepting help with new Locales in #117, so I have created a new Locale for Swedish. I've created sv-se.h and updated wrapper.h, CMakeLists.txt, appveyor and travis.
I've followed the guidelines on https://github.com/goatshriek/stumpless/blob/latest/docs/localization.md

[codecov]

Codecov Report

Merging #124 into latest will decrease coverage by 0.14%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           latest     #124      +/-   ##
==========================================
- Coverage   95.11%   94.97%   -0.15%     
==========================================
  Files          27       27              
  Lines        2068     2068              
==========================================
- Hits         1967     1964       -3     
- Misses        101      104       +3     

Impacted Files	Coverage Δ
src/target/file.c	87.03% <0.00%> (-1.86%)	⬇️
src/target.c	96.72% <0.00%> (-0.73%)	⬇️

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[goatshriek]

Excellent work, thank you so much for taking the time to make this contribution!