The existing price data APIs are unreliable during heavy load

[Cybourgeoisie]

Likely due to the recent surge in popularity, the APIs used by 10K Pizza are taking a very long time to respond - both CoinMarketCap's full listing and the real-time price information from CryptoCompare. Further, the real-time data from CC has been strongly manipulated in the past (DRGN still occasionally reports values $0.50 to $1.00 above or below its average on CMC; Golem had seen a ridiculous spike a few months back).

In lieu of writing a full API backend for use in 10K Pizza (or before considering taking on such a project), it would make sense to find ways to retrieve and cache the full listing, and to allow the CryptoCompare API to fail and fallback to our cached values when the load is too great.

1. Write a script to retrieve and cache the full listing from CMC every few minutes.
2. Update cryptofolio to use the cached values (and include a fail-safe that uses CMC if the values are too old).
3. Update cryptofolio to wait only a few seconds for CryptoCompare's data, and then cancel the requests (or re-issue them in the background) if the timing delay exceeds a threshold.

[MSFTserver]

maybe we could look into using something like ccxt libraries its packed with just about exchange and api