Update android-gradle-plugin version, add google() repos, ...#1

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vwmattr wants to merge 2 commits intoCasterIO:masterfrom

vwmattr:update-buildScripts

Commits on Oct 12, 2017

Update android-gradle-plugin version, add google() repos, update compile and target Sdk versions, update support version, update gradle version.
Reinman
committed
Lower compile and target Sdk version to 25, lower suport version to 25.4.0.
Reinman
committed