read environment variable that turns off/on --contracts

[gregwebs]

I already have code in place to automatically execute coffeescript that I don't want to change. This also makes it easy to define that there should not be contracts in the production environment.

What do you suggest for the variable name? CONTRACTS_COFFEE_ENABLED

--contracts on the command line would override this setting.

[disnet]

Good idea! That name is probably fine.

[gregwebs]

see #29