PostgreSQL packages for all currently supported branches

I think this is the optimal solution for packages of software with multiple supported versions, like MySQL, Ruby and PostgreSQL. Providing only one package for the latest version (like you did with your [Ruby package](http://chocolatey.org/packages/ruby) is dangerous and insecure in combination with Chocolatey’s keep-old-versions-design. I already explained the reasons more than once: https://github.com/chocolatey/chocolatey/issues/389#issuecomment-30451669, https://github.com/chocolatey/chocolatey/issues/259#issuecomment-23863107

This pull requests consists of the following packages:
* postgresql … Will always point to the latest stable versions of PostgreSQL (9.3.2) at the moment. If for example PostgreSQL 9.4 stable would be released, this package would update to it.
* postgresql-8.4 … Always the latest version of the 8.4.x branch (it’s 8.4.19 at the moment). This is good for folks whose apps aren’t compatible with newer PostgreSQL versions. But they will still receive 8.4.x security fixes.
* postgresql-9.0 … Same as before, but for the 9.0.x branch.
* postgresql-9.1 … Same as before, but for the 9.1.x branch.
* postgresql-9.2 … Same as before, but for the 9.2.x branch.
* postgresql-9.3 … Same as before, but for the 9.3.x branch. This package will currently provide the same version as the *postgresql* package, but it won’t upgrade to 9.4.x.

Note that a similar approach is currently used for packages for Linux distributions. For example, look at Debian: http://packages.debian.org/search?keywords=postgresql&searchon=names&suite=testing&section=all

To be more precise, my approach for the PostgreSQL packages is a combination of Debians slow and conservative release policy and Arch Linux’ always-latest-version policy (https://www.archlinux.org/packages/extra/x86_64/postgresql/), so it certainly satisfies **all** Chocolatey users.