Please update pyenv formula (v0.4.0-20130726 -> v0.4.0-20131023)

Please update `pyenv` formula. The changes in this release are below.

* pyenv: Improved [fish shell](http://fishshell.com/) support
* python-build: Add new PyPy releases; pypy-2.1, pypy-2.1-src,
* pypy3-2.1-beta1, pypy3-2.1-beta1-src
* python-build: Add ancient versions; 2.4, 2.4.1, 2.4.3, 2.4.4 and 2.4.5
* python-build: Add alpha releases; 3.4.0a2, 3.4.0a3, 3.4.0a4
* python-build: Update default pip version (1.4 -> 1.4.1)
* python-build: Update default setuptools version (0.9.7 -> 1.1.6)