title: Custom highlighter in ios-chart
body: <p>I am working on a custom chart, which is somewhat like scatter chart. I am plotting events against, date in x axis and time (24 hours) in y axis. So in a single day there can be multiple values in y axis. 
  I am done with the chart, but the highlighter does not work properly for obvious reasons. I was able to create my custom highlighter in android and assign that as a highlighter to the chart. But in the ios-library, the highlighter classes are declared as internal, and I cannot override the highlighter, OR assign a custom highlighter to the chart. </p>
  
  <p>How can I achieve this?</p>