Update INSTALL.txt
Update INSTALL.txt

removed Windows virtual box install
dimroc/tensorflow-mnist-tutorial,GoogleCloudPlatform/tensorflow-without-a-phd,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,dimroc/tensorflow-mnist-tutorial,dimroc/tensorflow-mnist-tutorial