test_vm - change vm box image (from CentOS 6.3 on dropbox to 6.5-based one on amazon)
test_vm - change vagrant box name (centos -> dbfit-test)
test_vm - customize vm RAM to 1GB
This is more portable across different boxes (i.e. the preset in current
box is ~512MB which leads to much swapping in case of full setup /incl.
Oracle/)