don't touch original req/res

[jonathanong]

would be nice if koa didn't touch the original req/res. since we're building a wrapper around them, i don't see why it would be necessary.

example is:

  /**
   * Set request URL.
   *
   * @api public
   */

  set url(val) {
    this.req.url = val;
  },

Wish it were something else like:

  get url() {
    return this._url || this.req.url
  },

  set url(val) {
    this._url = val
  }

[tj]

that would be nice in some ways, I've found in practice usually the only thing you really want "raw" access to that has not been modified is the original request url, I've never seen anyone manipulate request headers or anything like that, definitely would be bad practice at least. For now I don't think it's worth it but maybe in the future

[jonathanong]

yeah, this is the only case i can think of. if we don't edit req.url, we won't have to do any .originalUrl stuff, though you'll have to pass the mount points to sub apps somehow.

[jonathanong]

merging into #49