Specify currencies to be fetched

[emanuelconunaemme]

Instead of just fetching the first 5000, can we just just pass a list of symbols to fetch? Benefits:

1. Reducing API credits used
2. Reducing traffic
3. Allowing prices for currencies after #5000

Simple implementation: $CURRENCIES is set we hit v2/cryptocurrency/quotes/latest instead, passing it as CSV param.

If you are interested I can push a PR.

[bonovoxly]

Sure, looking to freshen this up in the coming months.