Added install generator to ease the setup

When you setup resque you have to do the same stuff as documented in the
readme, mostly line by line, so I moved it in a generator to be called
via resque:install.
Use a different redis db for test and development
Merge pull request #843 from sideshowcoder/48e842212e5e9cffc39dc628dc16a8cef09393e3

Add install generator for Rails