Draw temp graphs

Based on the pulled temp data, we can now draw graphs.

TODO list:
- Add time stamps on the X axis
- Add humidity data on the same graph
- Make graph zoom-able / scrollable
- Better fonts/legends
- Add a refresh button?

Signed-off-by: Prashant Malani <p.malani@gmail.com>
Minor styling fixes.

Signed-off-by: Prashant Malani <p.malani@gmail.com>