Address plugin ordering in README.md
Address plugin ordering in README.md

This plugin doesn't work if it is applied before the Android application or library plugins, as noted by issue #77.
MaTriXy/dexcount-gradle-plugin,MaTriXy/dexcount-gradle-plugin,benjamin-bader/dexcount-gradle-plugin,KeepSafe/dexcount-gradle-plugin,KeepSafe/dexcount-gradle-plugin,MaTriXy/dexcount-gradle-plugin,MaTriXy/dexcount-gradle-plugin,MaTriXy/dexcount-gradle-plugin,KeepSafe/dexcount-gradle-plugin,benjamin-bader/dexcount-gradle-plugin,benjamin-bader/dexcount-gradle-plugin