Pulls temperature data from XML file for a 7-day forecast
 - uses .xpath.each to go through XML file for each <time day="...."> tag
 - then traverses through child elements to find the <temperature day="..."> tags
 - traverses temp node to pull out "key" and "value" and save to hash
 - each day's temp hash is saved to an array
 - loops through array to display in a table