title: Importing a csv into d3; can't convert strings to numbers
body: <p>I have a csv file with data as follows:</p>
  
  <pre><code>Time, Conditions, Temperature, Humidity, WindDir, WindDeg, U1, Pressure, U2, U3, U4, U4, UV, U5, MoonPercent, SunriseHr, SunriseMin, SunsetHr
  "2014/06/19 19:00:00", "Clear", 16.8, "87%", "North", 355, 8.0, "1010", "11", 15, "NA", "1.2", " 0", "11", "47", "5", "03" "22", "07"
  "2014/06/19 19:31:01", "Mostly Cloudy", 17.2, "86%", "NNE", 26, 12.9, "1010", "11", 15, "NA", "0.7", " 0", "11", "47", "5", "03" "22", "07"
  "2014/06/19 19:40:00", "Mostly Cloudy", 17.4, "85%", "ENE", 68, 6.4, "1010", "11", 15, "NA", "0.7", " 0", "11", "47", "5", "03" "22", "07"
  </code></pre>
  
  <p>I want to import it and have array contain the numbers as numbers, not as strings as it does at first:</p>
  
  <pre><code>Object { Time="2014/06/19 19:00:00", Conditions=" "Clear"", Temperature=" 16.8", more...}
  </code></pre>
  
  <p>The problem is, no matter what I try I've not been able to turn the numbers into actual numbers, just NaN. Here's my import code:</p>
  
  <pre><code>d3.csv("weatherLog.csv", function(error, csv) {
          if (error) return console.warn(error);
  
          csv.forEach(function(d){ (d['Temperature'] = +d['Temperature']); });
          console.log(csv);
  </code></pre>
  
  <p>I tried d.Temperature instead, I tried parseInt(d.['Temperature']) instead, but nothing works out, and of course d3 can't use a string (or a NaN) as data so I need to convert this first somehow. I tried manually removing the space from the CSV file (so the imported string was "16.8" rather than " 16.8") but that didn't help either...</p>