Remove RxLint

[danielgomezrico]

Related to:
https://bitbucket.org/littlerobots/rxlint/issues/26/some-version-break-with-projects-that-uses

Newer RxLint requires you to use the new android gradle plugin (3.x) to work, creating a crash on compilation otherwise.

[codecov]

Codecov Report

Merging #69 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##             master     #69   +/-   ##
========================================
  Coverage      8.33%   8.33%           
  Complexity       39      39           
========================================
  Files            16      16           
  Lines           720     720           
  Branches        116     116           
========================================
  Hits             60      60           
  Misses          620     620           
  Partials         40      40

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