ETHLDN#71

The full diff is at v0.8...v0.8.2

smart contracts

• fix Contract can be drained if event cancelled vulnerability (v0.8.1) PR
• stop returning ether back to user when exception is raised PR

config

• upgrade web3 from 0.16 to 0.20
• add app_config.js to hard code contract addresses (and prompt for "yes" confirmation)

tests

• change stress test to log attend function by admin (aka batchAttend)
• change stress test to log confirmation#add function

scripts

• change scripts/decrypt.js to take block number as argument
• change scripts/decrypt.js to take contract address

frontend

• switch ethereum price API from cryptocompare to coinmarketcap
• change button from Register to RSVP
• change button from Attend to Confirm Attendance