function Buffer(target, type, gl) {
    this.buffer = null;
    this.target = target;
    this.type = type;
    this.data = [];
    this.gl = gl;
}
Buffer is a private class that wraps the vertex data that defines
the the points of the triangles that webgl draws. Each buffer
maps to one attribute of a mesh.

@class Buffer
@constructor

@param {Number} target The bind target of the buffer to update: ARRAY_BUFFER or ELEMENT_ARRAY_BUFFER
@param {Object} type Array type to be used in calls to gl.bufferData.
@param {WebGLContext} gl The WebGL context that the buffer is hosted by.

@return {undefined} undefined