[#201] Implemented route for news cluster feature

[alvyn279]

• Modified sample flask application to support a root route and a news clusters route
• Added tests
• Sample news cluster route usage: http://localhost:8080/news_clusters/1581735096?direction=1&quantity=20
• Sample response:

  {
  "clusters": [{
    "articles": [
      {
        "article_url": "https://www.fool.com/investing/2020/02/18/better-buy-apple-vs-google.aspx", 
        "date": "Tue, 18 Feb 2020 07:45:00 -0500", 
        "image_url": "https://cdn.snapi.dev/images/v1/k/8/stocks1-2.jpg", 
        "sentiment": "Neutral", 
        "source_name": "The Motley Fool", 
        "summary": "Size isn't necessarily everything to investors, of course. The case for, and against, Apple It's a name that needs no introduction. But there's the rub, so to speak. In the meantime, YouTube's advertising prowess is tremendous. It generated $4.7 billion in revenue last quarter just by showing ads before, during, or after videos. It's not an easy choice. Tax implications must always be considered, and if any stock can defy the odds, it's Apple.", 
        "tickers": [
          "AAPL", 
          "GOOG", 
          "GOOGL"
        ], 
        "timestamp": "1582029900", 
        "title": "Better Buy: Apple vs. Google"
      }
    ], 
    "size": 1, 
    "timestamp": 1582029900
  }, 
  {
    "articles": [
      {
        "article_url": "https://www.marketwatch.com/story/apple-set-to-lose-title-of-most-valuable-us-companies-to-microsoft-2020-02-18", 
        "date": "Tue, 18 Feb 2020 07:57:03 -0500", 
        "image_url": "https://cdn.snapi.dev/images/v1/1/0/103922274-rtx2ojun-3.jpg", 
        "sentiment": "Negative", 
        "source_name": "Market Watch", 
        "summary": "With Apple Inc. shares AAPL, +0.27% falling 3.1% in premarket trading Tuesday, Microsoft Corp. MSFT, -0.15% is on track to take back the No. 1 position on the list of the U.S.'s most valuable companies by market capitalization. Microsoft's stock is down 0.2% ahead of the open, which means the software giant is headed toward a market cap of $1.408 trillion at the open, while Apple is on track to open with a market cap of $1.378 trillion. The last time Microsoft closed as the most valuable company was Feb. 11 and Feb. 10, which ended a 67-session run with Apple at No. 1. The companies were still well ahead of third-place Amazon.com Inc. AMZN, +0.41% , which closed Friday with at market cap of $1.063 trillion, and fourth-place Alphabet Inc. GOOGL, +1.46% at $1.044 trillion.", 
        "tickers": [
          "AAPL"
        ], 
        "timestamp": "1582030623", 
        "title": "Apple set to lose title of most valuable U.S. companies to Microsoft"
      }
    ], 
    "size": 1, 
    "timestamp": 1582030623
  }
  ], 
  "next_timestamp": 1582031280, 
  "timestamp": 1581735096
  }

[alvyn279]

Looks good, whatever I had noticed Chirac brought up already. Just wondering if there were constants used in BE for making it more verbose instead of -1 and 1

I think 1 going forward in time and -1 going backwards in time speaks for itself. But good point, im actually gonna include a docstring

[Lercerss]

Could you unify the types for timestamp in the JSON response? You have both string and number