title: Modifying a pdf using Hummus and creating buffer
body: <p>I'm modifying a pdf using the code below but struggling with how to create a buffer that can then be used as an email attachment without writing anything to disk.</p>
  
  <p>I'm finding it hard to work out from the documentation.</p>
  
  <pre><code>    var pdfWriter = hummus.createWriterToModify(__dirname + '/voucher.pdf', needToCreateBuffer);
  
      var pageModifier = new hummus.PDFPageModifier(pdfWriter, 0);
      var fontOswald = pdfWriter.getFontForFile('.fonts/Oswald-Bold.ttf');
      pageModifier.startContext()
          .getContext()
          .writeText(
              '£100',
              296, 105, {
                  font: fontOswald,
                  size: 70,
                  colorspace: 'gray',
                  color: 0x00
              }
          ).writeText(
              'CODE: GHGJHJHH',
              296, 80, {
                  font: fontOswald,
                  size: 18,
                  colorspace: 'gray',
                  color: 0x00
              }
          );
      pageModifier.endContext().writePage();
      pdfWriter.end();
  </code></pre>