Update binary vendoring steps in README

For Apache 2.2.25 and PHP 5.3.27.

As of now, the vendoring can now be done in a blank dyno rather
easily.  This process is now explained explicitly in the README.

The following is an overview of some of the changes:

* Rewrite recipes into bash-script form

* Make re-entrant (via clearing /app) for easier iteration

* Use variable substitutions for version, directory, and archive names
  instead of repeating chunks of each all over the place.

* Make downloading optional, again to assist iteration.

* Silence GNU Make steps via '-s' to quiet down builds (warnings are
  still shown).

* Rely on the bash-ism pushd and popd to be more robust to slight
  changes in relative paths that may occur in the future.

* Rely on the PHP-distributed version of PEAR/PECL rather than the
  apt-get install version, which has a more dubious set of default
  paths and can't be done in-dyno.  This makes the steps for dealing
  with 'APC' much simpler.

* Use default responses for prompts when building APC rather than
  prompting the builder.

* Sanitize cgi-bin of default Apache programs.

* Create binary-vendoring tarballs with the same name that they are
  intended to be uploaded as.

  Notably, name of the tarball and the directory contained within that
  tarball will not match because the contained directory is devoid of
  version numbering, unlike the name of the tarball.