Add a nice wrapper for get_sys_info

[nahla-nee]

Implements a nice safe wrapper for get_sys_info as described in #839 .

[thejpster]

Thank you for this PR. In general it looks great!

I would like to see an example of using this API though.

[nahla-nee]

Sure! And I'll go ahead make the suggestions changes too. I'll probably do that by tonight (us time). Do you want the example to be added to the existing rom function example? And if so do you want it to replace the existing one?

[thejpster]

I'm ok with it going into the existing example binary. I'm not sure if we need to leave an example of the old API or if we expect people to only use the new one.

[nahla-nee]

I also went ahead and added some more documentation. It probably could use more work cause I was in a bit of a rush but it should make things easier to read. I also elaborated on the existing examples since we don't have settle for printing the hex representation of the bytes get_sys_info gives back now.