add makefile release task

Added simple release task to `Makefile`, replaces occurrences of last git tag (`git describe --abbrev=0 --tags`) in `README.markdown` and `install.sh` with supplied `TAG` variable and tags the repo with supplied tag:

```sh
make release TAG=v0.11.0
```
But I see `package.json` does, but without the `v` prefix. Can we add the `v` there as well?