Updated Readme.md
Updated Readme.md

The SBT plug-in is no longer required as it is included in the Scala plug-in. Also the Android plug-in is necessary or else IDEA won't actually show any file in the imported project. See http://stackoverflow.com/questions/29719394/how-to-get-intellij-idea-14-working-with-scala-on-android-sbt for details.
wpc009/android-sdk-plugin,adsinc/android-sdk-plugin,pfn/android-sdk-plugin,aafa/android-sdk-plugin,zbsz/android-sdk-plugin,pfn/android-sdk-plugin,dant3/android-sdk-plugin,zbsz/android-sdk-plugin,adsinc/android-sdk-plugin,aafa/android-sdk-plugin,dant3/android-sdk-plugin,aafa/android-sdk-plugin,wpc009/android-sdk-plugin,pfn/android-sdk-plugin