A few small (compatible) changes: CN server, --remaining, time argument "fix", getTimeOffset

Firstly, I realise these changes are not related to one another and would better be in separate merges. However, they are small compatible changes I made mainly for my own use.

Summary (might as well have listed the commit messages, oh well):

* Pulled in the actual additions of https://github.com/wolftankk/python-bna/commit/079ef3a1873ce1fe834b836ea871d487917dde24 (without all the whitespace changes);
* Added a `--remaining` option to display `12345678 (25s remaining)` rather than just the token, for the command line tool;
* Changed the `time` argument to `getToken`, so `time.time()` is evaluated every time instead of once;
* Added a simple `getTimeOffset` function to the library, probably unnecessary for most hosts, but I use it anyway.