chacha20poly1305: aead crate upgrade

[tarcieri]

Upgrades to the aead v0.3.0-pre crate.

[codecov-commenter]

Codecov Report

Merging #144 into master will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #144      +/-   ##
==========================================
+ Coverage   94.17%   94.21%   +0.03%     
==========================================
  Files          29       29              
  Lines         756      761       +5     
==========================================
+ Hits          712      717       +5     
  Misses         44       44              

Impacted Files	Coverage Δ
chacha20poly1305/src/cipher.rs	93.75% <100.00%> (+0.64%)	⬆️
chacha20poly1305/src/lib.rs	76.92% <100.00%> (+1.92%)	⬆️
chacha20poly1305/src/xchacha20poly1305.rs	66.66% <100.00%> (+3.03%)	⬆️
chacha20poly1305/tests/lib.rs	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update fed6ce8...58f4d3f. Read the comment docs.