Incremented buildToolsVersion to 20.0.0
Merge branch 'hotfix/2.15.13' of https://github.com/shouldit/android-proxy into hotfix/2.15.13

# By Marco Pagliari
# Via Marco Pagliari
* 'hotfix/2.15.13' of https://github.com/shouldit/android-proxy:
  Switched platform-tools with tools dependencies order
  Update .travis.yml
  Update circle.yml