title: Using more than 2 marker presets
body: <p>I want to use 3 markers in a script. I've started to use Kanji and Kiro marker preset without problem.
  When i've started to add a third marker (a pattern with letterA.patt file via ar.js url), google chrome (and firefox) complained about a memory problem !
  The only solution founded was to modify aframe-ar.js and added letterA as marker preset, like Kiro and Kanji.
  Question1: what about that memory problem with my pattern ?
  Question2: why not added more marker preset (letterD...) by default in aframe-ar.js ?</p>
  <p>Best regards,</p>
  <p>Emmanuel</p>