Replace travis script to fetch configlet

bin/fetch-configlet

 LATEST=https://github.com/exercism/configlet/releases/latest
 
 VERSION="$(curl --head --silent $LATEST | awk -v FS=/ '/Location:/{print $NF}' | tr -d '\r')"
-URL=https://github.com/exercism/configlet/releases/download/$VERSION/configlet-linux-amd64.tgz
+URL=https://github.com/exercism/configlet/releases/download/$VERSION/configlet-linux-64bit.tgz
 
 curl -s --location $URL | tar xz -C bin/