xrp-price-aggregate@0.0.15

[yyolk]

this addresses a step missing in 0.0.14; it was non-breaking as the result was the same as the prior 0.0.13 release of any exceptions.

the summary is identical to #43

starts to address #27 - by filtering out at the time of failure any chains of providers requests.
Platforms that respond to at least the initial request will be included in the aggregate results

i.e.:

[ ❌ ] <~ won't be included
[ ✅ ✅ ❌ ] <~ will be included 👍 
[ ✅ ❌] <~ will be included 👍
[ ✅ ✅ ✅ ] <~ will be included 👍

see yyolk/xrp-price-aggregate#20 https://github.com/yyolk/xrp-price-aggregate/releases/tag/0.0.15 for more info