Update build.gradle

[rogerhu]

Move to using AARs instead of JAR

[codecov]

Codecov Report

Merging #50 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #50   +/-   ##
=========================================
  Coverage     67.13%   67.13%           
  Complexity       78       78           
=========================================
  Files            11       11           
  Lines           359      359           
  Branches         24       24           
=========================================
  Hits            241      241           
  Misses          104      104           
  Partials         14       14

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