postgresql 9.4rc1

Also I noticed installing this via `--devel` does not seem to register with `homebrew` as installed, so packages requiring `postgresql` will try to install the `stable` version...

```
$ brew info postgis
postgis: stable 2.1.4, HEAD
http://postgis.net
Not installed
From: https://github.com/Homebrew/homebrew/blob/master/Library/Formula/postgis.rb
==> Dependencies
Build: pkg-config ✔, gpp ✔
Required: postgresql ✘, proj ✔, geos ✔, json-c ✔
```