Use tput instead of clear. Closes #196

Instead of clearing the screen, use `tput smcup` and `tput rmcup`.

Screenshots:
![n-screenshot-1](https://cloud.githubusercontent.com/assets/4295266/4782786/8b61457a-5d06-11e4-823e-558b639a4235.png)
![n-screenshot-2](https://cloud.githubusercontent.com/assets/4295266/4782787/8f027640-5d06-11e4-9a66-7ad6e83808fb.png)
![n-screenshot-3](https://cloud.githubusercontent.com/assets/4295266/4782788/9171ff9a-5d06-11e4-9b53-1819d498afc4.png)