make mooncalc to support exact time, not just beginning of the day

[gre]

I've taken some subjective decision, feel free to take or discard this PR:

• directly exposes the function. (making this a breaking change, we can have backward support with some effort, otherwise this needs to go in a major semver change)
• no longer returning date (redundant)

note: this does not seem to fix https://github.com/giboow/mooncalc/issues/2 . I didn't really tested yet if the constellation is correct against a trusting website, do you know any good one to test against? cc @vicesalles

[lgaspari]

Hi @gre I'm trying to do some follow-up on this project which I found really useful but it seems it cannot be trusted according to Moon Calendar from astro-seek webpage (at least the zodiac sign part). I applied the changes from both PRs (#3 and #4) and none of them seems to make any great changes.

Additionally, the open issues #1 #2 makes me wonder what else could be wrong in the code, and I'm just a beginner in astrology, so I couldn't figure out what.

@giboow is there any change you could resume this project?