Refactor render core
  1.  implement renderDOMLine
  2.  add AnsiColorState, an object that tracks ansi foreground/background/bold
  3.  move output parser into render.coffee
  4.  move escapeHtmlEntities into render.coffee
  5.  refactor ansi color parsing from mud_client.js into render.coffee
  6.  rename ansi color css class from "tnc" (why was it named that?) to "ansi_color"
  7.  renderDOMLine and AnsiColorState now used in client.js