Fixed typo in README ("powerfull" => "powerful")
Fixed typo in README ("powerfull" => "powerful")

Closes #614

iamrahulroy/retire,mavenlink/retire,doximity/tire,rubydubee/retire,tklee/tire_shiphawk,1776/tire,HenleyChiu/tire,zaharpecherin/retire,ChapterMedia/tire,elbuo8/retire,brijeshgpt7/retire,karmi/retire,dbose/retire,fabn/retire,Telmate/tire