added ANDROID_HOME tip to README
added ANDROID_HOME tip to README

baberthal/ruboto,lucasallan/ruboto,ruboto/ruboto,Jodell88/ruboto,lucasallan/ruboto,baberthal/ruboto,Jodell88/ruboto,baberthal/ruboto,ruboto/ruboto,Jodell88/ruboto,lucasallan/ruboto,ruboto/ruboto