Don't parse dates as prices

[kmike]

Dates like July, 2004 or 15.08.2017 should not be parsed as prices, we should detect them and return amount=None currency=None.

[GodSaveTheDucks]

Can we find a universal date parser lib and filter the matches? If that's a good approach I would like to work on it.

[kmike]

@GodSaveTheDucks there is https://github.com/scrapinghub/dateparser, but I think it is better not to follow this approach, for performance and simplicity reasons. It is not a job of price-parser to classify prices vs dates with a highest possible quality; the idea is to have some additional pre-filter, which is fast & reliable, but likely not complete.

[bulatbulat48]

@GodSaveTheDucks there is https://github.com/scrapinghub/dateparser, but I think it is better not to follow this approach, for performance and simplicity reasons. It is not a job of price-parser to classify prices vs dates with a highest possible quality; the idea is to have some additional pre-filter, which is fast & reliable, but likely not complete.

@kmike Code review please: #19
thanks!

[bulatbulat48]

@kmike tests fixed. Take a look, please.