Fix trash.rb formular

Hi 

I tried to install this formular when I encountered the following problem:

```bash
itiny:~ alex$ brew install trash
==> Cloning http://hasseg.org/git-public/trash.git/
Error: Failure while executing: git clone --branch v0.8.2 http://hasseg.org/git-public/trash.git/ /Library/Caches/Homebrew/trash--git
```

Some how my installation was not able to clone this repository. I also discovered that the official repository is now on Github as stated on the website.

I also changed the formular to grep the archive via file download instead of the git repository and bumped the version number from v0.8.2 to v0.8.3.