Add get_bin command to retrieve binary data without trailing \n

[vi]

I'm not sure if this is a correct implementation. Related to #52.

[heapwolf]

I like this idea actually (more than setting the encoding, for this use case). Maybe we could take this a step further and print the hex value, ie:

>getbin foobar
[12 05 e4 6f 11 b5]