Update version in AndroidManifest.xml

rake-update-version-android-manifest.rb

task :update_build_number do
    File.open('AndroidManifest.xml', 'r+') do |f|
        manifest = f.read

        build = ENV['TRAVIS_BUILD_NUMBER'] || 0
        # Update version
        manifest = manifest.gsub(
            /android:versionCode=".*"/, "android:versionCode=\"#{build}\"")

        # Write back
        f.rewind
        f.truncate(0)
        f.write(manifest)
    end
end