Regenerate the iOS sender at every call

[flovilmart]

Should mitigate issue #90

[codecov]

Codecov Report

Merging #104 into master will decrease coverage by 1.87%.
The diff coverage is 75%.

@@            Coverage Diff             @@
##           master     #104      +/-   ##
==========================================
- Coverage     100%   98.12%   -1.88%     
==========================================
  Files           5        5              
  Lines         256      266      +10     
==========================================
+ Hits          256      261       +5     
- Misses          0        5       +5

Impacted Files	Coverage Δ
src/APNS.js	96.09% <75%> (-3.91%)	⬇️

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