Moved game control into GameManager and saving.

Created GameManager.js to control the flow of the game and handle saving
progress. Added save() function to store wallet status and also
implemented loading progress from localStorage.
Added ability to purchase miner upgrades.
Added market.js and buy/sell function.

Player can now buy and sell whole bitcoins.
Added saving of miner, autostart of mining
Merge pull request #3 from DylanDavidson/dylanworking

Reorganization of code, and basic features implemented.