title: Plot.ly: Simple prefix or suffix for hover text
body: <p>I've tried reading the documentation but I haven't found a simple way to add a suffix to a hover text.
  Is there a way to add text to the <code>hoverformat</code>? For example <code>y respondents</code> where y is the y value.</p>
  
  <p>The setting <code>yaxis: {hoverformat: ''}</code> does not seem to allow strings?
  I'm used to working with FlotChart where you can simply put <code>"%y respondents"</code>.</p>
  
  <p>Any help is much appreciated.</p>