swap out lazsysodium for tweetnacl

[daniellevass]

Description of the pull request

Lazy Sodium was causing crashes on Android because it included jna which didn't have the right interpreters. This would have been kinda complicated to include the right ones depending on how people were using the channels java client so we've gone with another solution.

[codecov-commenter]

Codecov Report

Merging #271 into master will decrease coverage by 20.49%.
The diff coverage is 100.00%.

@@              Coverage Diff              @@
##             master     #271       +/-   ##
=============================================
- Coverage     65.92%   45.43%   -20.50%     
- Complexity      261      284       +23     
=============================================
  Files            31       31               
  Lines          1130     3053     +1923     
  Branches         95      254      +159     
=============================================
+ Hits            745     1387      +642     
- Misses          339     1610     +1271     
- Partials         46       56       +10     

Impacted Files	Coverage Δ	Complexity Δ
...a/com/pusher/client/crypto/nacl/TweetNaclFast.java	33.50% <ø> (ø)	26.00 <0.00> (?)
...com/pusher/client/crypto/nacl/SecretBoxOpener.java	76.47% <100.00%> (ø)	3.00 <0.00> (ø)

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