vision/image: fixed incorrectly deleting return tensor

updated script and README.md; bump version v0.3.9.rc1

chores(bump version)

bump new version

feat(dutil): added DataSet and DataLoader

fixed incorrect url in README setup.sh

resolved sugarme#4 and bump version

chorus: bump version v0.3.3

tensor/print: added padding and precision

more changes to pointer receiver at nn sub-package and clean-up retur…

…n variable