[Issue #22] consider time as local if no offset is given

[robuye]

it uses ENV['TZ'] or can be passed as an option (global), if something goes wrong (no env var or unknown timezone) it will fallback to UTC. It's not perfect, but i don't have better idea.

Added facets/date dependency.
Also added pry as development dependency, its really helpful.

[rubiii]

the return value is not used, so i would change to code to not look like it matters:

ENV['TZ'] = tz if tz

[rubiii]

thanks @robuye!

can this change be backed by a specification? that would be something to put in the changelog for everyone to follow through as this change probably affects a lot of people. also, timezone changes might not break people's tests and they surely don't expect them. there are people that don't review libraries before updating and this could possibly result in very nasty surprises.

what do you think? what do others think?

[robuye]

good point about affecting others, I didn't think about it.
As @cschiewek described, ISO8601 specifies that timezone without offset should be considered as local:

(...)Without any further additions, a date and time as written above is assumed to be in some local time zone.

I think it would be good idea to wait some time and possibly get feedback, this is not an urgent fix.

[rubiii]

good idea. thanks.