Simplified project layout and updated dependencies

I'm setting my own URL shortener service (in [qn.pw](http://qn.pw), which belongs to [Qomun](http://en.qomun.com)) and I found shawty to be no go-get-friendly, so I fixed the project using project layout described in [Golang docs](http://golang.org/doc/code.html).

I also changed dependencies to current repositories (pq is now at https://github.com/lib/pq and go-sql-driver at https://github.com/go-sql-driver/mysql - all in lowercase).