minor changes to installation instructions
minor changes to installation instructions

Change-Id: I7658fa39aca1466f904b3765966dcfef0125324a

dimroc/tensorflow-mnist-tutorial,dimroc/tensorflow-mnist-tutorial,dimroc/tensorflow-mnist-tutorial,dimroc/tensorflow-mnist-tutorial,dimroc/tensorflow-mnist-tutorial,GoogleCloudPlatform/tensorflow-without-a-phd,dimroc/tensorflow-mnist-tutorial,GoogleCloudPlatform/tensorflow-without-a-phd,GoogleCloudPlatform/tensorflow-without-a-phd,GoogleCloudPlatform/tensorflow-without-a-phd