Choice of Shop or Upgrade!

Added an option to either enter the Relic Shop or choose an extra Upgrade every 5 rounds instead of just forcing players into the Relic Shop.

At early levels it's pretty rare to have enough cash for relics and visiting the shop could be frustrating, hopefully now those extra upgrades will come in handy.

Also testing out builds for Linux and Mac so everyone can drop some balls together.

See how things feel, report all the bugs!