A way to force all dependencies for android support to follow a single version (in this case 25.4.0) without using tools:replace.

build.gradle

// from https://stackoverflow.com/questions/43280871/android-getting-manifest-merger-failed-error-after-updating-to-a-new-version
// to force everything to use 25.4.0 instead of dealing with merge conflict on 26.1.0
configurations.all {
    resolutionStrategy.eachDependency { DependencyResolveDetails details ->
        def requested = details.requested
        if (requested.group == 'com.android.support') {
            if (!requested.name.startsWith("multidex")) {
                details.useVersion '25.4.0'
            }
        }
    }
}