code: function(unit) {
  		var gl = this.gl;
  		if (unit || unit === 0)
  			gl.activeTexture(gl.TEXTURE0 + unit);
  		gl.bindTexture(this.target, this.id);
  	}
docs: Binds the texture. If unit is specified,
  it will bind the texture at the given slot
  (TEXTURE0, TEXTURE1, etc). If unit is not specified,
  it will simply bind the texture at whichever slot
  is currently active.
  
  @method  bind
  @param  {Number} unit the texture unit index, starting at 0