Incorrect return value from `trits_from_int(0)`

[todofixthis]

trits = iota.trits_from_int(0)
print trits
> []

normal print:

trits = iota.trits_from_int(1)
print trits
> [1]

So I would expect:

trits = iota.trits_from_int(0)
print trits
> [0]

[todofixthis]

There's a lot of existing functionality that relies on trits_from_int(0) returning an empty list; this will not be a trivial change.

I'll look into this a bit, see if that functionality can be modified to expect [0] instead, or at worst we could add an argument to the function that determines how to handle 0.

[todofixthis]

Scheduled for release: 2.0.1