installer documentation in contiv website.

[gaurav-dalvi]

Following things need to be added.
Whatever content goes in for these issues

1: contiv/install#49
2: contiv/install#46
3: https://github.com/contiv/install/blob/master/QUICKSTART.md
4: https://github.com/contiv/install/blob/master/README.md
5: https://github.com/contiv/install/blob/master/install/ansible/install_swarm.sh

Please feel free to add more details.