fix pages

Howdy @erobinson,

Sorry about the trouble with pages.
It looks like your branch is mostly up to date, my earlier "fix" was actually not a fix.

Pretty sure the last commit in here does fix things, I can see output like this now:

```bash
$ mm-send-comm.py --serial 665455 tweak ReadGlucoseHistory --page  1 --save 
```

Which saves this file: `ReadGlucoseHistory-page-1.data` (before it would save `-page-0.data` regardless of which page you asked for.  Sorry about that!

Let me know if you need any help, but you seem to be doing things quite well on your own.