v0.2.0: security updates

This release mostly brings security updates and bugfixes, such as:

• the signed stateRoot is now generated by hashing the balanceTree together with the channel ID, as per protocol spec
• the follower does not accept the NewState if it doesn't have a valid signature (this check is redundant but nice to have, as we're also checking on POST validator-messages)
• a vulnerability where you can trick the follower into signing an invalid state (#56) is fixed
• you can now get event aggregates via the event-aggregates API (useful for analytics)

Remaining features until we reach a production level:

• Heartbeat message: #17
• Min price per impression: #20
• Validator fees: #14
• Restructure event aggregates: #50

for more details, see the release-1 milestone: https://github.com/AdExNetwork/adex-validator-stack-js/milestone/2

v0.1.0: closer to usable

This release brings:

• a critical fix in the getHealth logic
• a critical crash in channel routes fixed
• integration test suite: #1
• more advanced REST API

Remaining features until we reach a production level:

• Heartbeat message: #17
• Min price per impression: #20
• Validator fees: #14

First proof of concept: "No Nick" v0.0.1

This marks the first PoC of the AdEx Validator stack.

it is, of course, Nickless

It implements:

• The Sentry node, with efficient and horizontally scalable event tracking (using the eventAggr pattern)
• The Validator Worker, which checks the correctness state transitions, and signs a new NewState message (if leader) or ApproveState message if follower; this component has been verified to correctly detect invalid state transitions (cheating attempts from either leader or follower)
• ethereum and dummy adapters

Next milestones until the first usable PoC:

• Stricter auth token checking
• Validator Init message
• Ethereum Watcher: watch for new channels and write them to the DB
• Unit tests for the adapters and producer, leader, follower
• setup wrk-based bench utilities