Price suggestions

[AnssiAhola]

I added this API point that was missing as was pointed out in the discussion #68

Also added year property that was missing from the Master class. #67 comment
I think this fix is so small that it can be clumped with the new API. What do you think @JOJ0 or @alifhughes ?

This still needs documentation for the new API point. I'll come back to that at some point.

Also any feedback is appreciated 😄

[JOJ0]

Will have a look tomorrow, I promise! Want to quickly try it out. I am sure it's fine already though :-) Very nice and useful feature! Thank you for adding! Great!

Adding the tiny change year prop to this PR is perfectly fine for me.

[JOJ0]

Hi Anssi,
I shouldn't ever promise when it's coming to dates and times I guess :-))

I played around a little. Single release straight forward. Eg:

>>> release = d.release(12345)
>>> release.price_suggestions
<PriceSuggestions Price for Mint (M) is <Price 12.852941176470587 'EUR'>>

>>> release.price_suggestions.very_good_plus
<Price 8.794117647058822 'EUR'>

>>> release.price_suggestions.very_good_plus.value
8.794117647058822

What I noticed, but I think this has nothing to do with your implementation but is a general odd thing in p3dc, when I use search, I seem to find master releases and those don't have certain attributes available including the price_suggestions:

>>> results = d.search("chaos theory amon tobin")
>>> for result in results: print(result.title, result.year, result.genres)
# ...
# Loads of results, all fine.
# ...

>>> for result in results: print(result.companies)
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Master' object has no attribute 'companies'
>>>

>>> for result in results: print(result.price_suggestions)
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Master' object has no attribute 'price_suggestions'
>>>

[JOJ0]

Ah ok I get it, when I do a regular search I get master releases and regular releases in my result. In that case, the very first is a master release, the one's after that are regular one's:

https://www.discogs.com/search/?q=chaos+theory+amon+tobin&type=all

So yes, that's all expected behaviour I guess. All good, I think we could merge this. Docs another time :-)