Fix TypeError: can't concat str to bytes.

[jgoclawski]

Handle invalid use of the library.

When TypeError: can't concat str to bytes happens it's probably because something like this was used:

api.get_binary_resource('/').call('ping', { 'address': '192.168.56.1', 'count': '4' })

When using get_binary_resource then the values should be bytes, they should be encoded. In this case, let the library handle encoding/decoding and use get_resource instead:

api.get_resource('/').call('ping', { 'address': '192.168.56.1', 'count': '4' })

The first version (with get_binary_resource) will now work, thanks to this PR, but emit a warning.

Fixes: #39
Supersedes: #65