CC-5 - Setup test cases with PHPUnit for RSI

[sjason19]

Context: Setup test cases for RSI.

Procedure: Make a test JSON data set in this format: https://min-api.cryptocompare.com/data/histoday?fsym=ETH&tsym=BTC&limit=30&e=CCCAGG and manually calculate the RSI values yourself and compare the algo output with your output.

Expectation: The correct RSI value is calculated