serialOpen not working on Resin.io

Hi,

I am trying to use Bonescript on a BeagleBone black running [resinOS](https://resinos.io/). I install it with yarn, and then import it using a typical require statement. Calls to `pinMode` and `digitalWrite` are working fine. I encounter issues with `serialOpen` when I do:
```
bonescript.serialOpen('/dev/tty04', { baudRate: 112500 });
```
This returns the error:
```
TypeError: Cannot read property 'path' of undefined
at Object.newFunction [as serialOpen] (/usr/src/app/node_modules/bonescript/src/my.js:451:31)
at Object.m.doOpen (/usr/src/app/node_modules/bonescript/src/serial.js:16:28
```

I took a look at the source and couldn't seem to figure out what was happening with the path property. I have tried different options, different ttys, and dropping the leading zero in the port to no avail. Any help is greatly appreciated!

Start by reading src/my.js around line 451 and src/serial.js around line 16, then reproduce serialOpen on a BeagleBone Black running resinOS with the reported device paths and options. Done means identifying why the path property is undefined and verifying that serialOpen works with the supported port configuration.

Written by the indexing model from the issue text.