MongoDB, some anti-bot measures, improved scraping logic and proxy support

NOTE: We're moving from Redis to MongoDB. There's no conversion tool for in-place upgrades.

• Move from Redis to MongoDB
• Update scraping logic
• Improve proxy support
• Add some anti-bot detection measures
• Thanks to @iloveitaly for these changes!

Fix proxy support in checks

Fix to #33 (#35)

* Readme

* Fix to #33 (#34)

Add proxy support

 [3.2.0] Adding proxy support (#32)

* Adding proxy variable to config

* Update constants.js

* export proxy var

* adding proxy support to get-price.js

Fix break

[3.1.3] Fix break (#22)

### [3.1.3] - 2018-6-14
- Flight data loaded after page is loaded - added wait for .flight-stops selector
- Change URL to current format
- Fix test to handle case of no prices found
- Add tests for expected bad inputs

[3.1.2] (#19)

• Add unit test for Alerts
• Add additional logging and error handling
• Attempt to reduce memory usage by manually calling about:blank prior to closing page
• Add protocol to email link

3.1.1: Add Semaphore to limit simultaneous pages (#11)

• Fix bug with crash when email or phone number is not set but respective service is enabled
• Add semaphore to limit number of pages open at once - hopefully fixing the "Error: Page crashed" error. Limited to 5 pages. Defaults to 5 pages at once - set ENV.MAX_PAGES to change.

UI enhancements

UI enhancements (#10)

* Add check for invalid ID, display error if invalid parameters

* Update version history

Fix for Heroku deployment errors and reduce memory usage

• Avoid multiple browser instances during task:check - reduce memory usage
• Add nodejs buildpack for Heroku deployment

Support new SW site redesign

Switched from osmosis to Puppeteer/Chrome

NOTE: Heroku deployments must add https://github.com/jontewks/puppeteer-heroku-buildpack as a buildpack prior to deploying (only if redeploying)

2.1.0

Add support for checking for the cheapest flight on a day