chore: bump version to 1.6.0

[1.6.0] - 2018-04-21

Added

• Support viewport and skipRequestedRedirect for crawler.queue()'s options.
• Emit requestdisallowed event.
• Make onSuccess pass redirectChain in the response.

changed

• Bump Node.js version up to 8.10.0.
• Update Puppeteer version to 1.3.0.
• Move node_redis to the peer dependencies.
• Make crawler.queue() to return Promise.

Fixed

• Fix a bug of silently failing to insert jQuery due to CSP.