fix typos for starting play in production

Hi,

at least on my machine (Linux Mint 13) `RACK_ENV` was never set in `script/web` unless i add `export` . 
The server never ran as daemon and therefore could not be stopped with `script/play stop`. 
In production the process list now shows `thin server` which is correct according to the `thin`-changelog:

`Set process name to 'thin server (0.0.0.0:3000)' when running as a daemon` .