Callattendant Release v2.1.0

Minor release to introduce an upgraded web server and a couple of fixes.

Changes:

• Replace embedded development WSGI server in Flask with Waitress (asynchronous threads)
  No more Flask dev mode warnings.
• Update NOMOROBO processing to classify current query return data better (@telnetdoogie)
• Added validation routines to handle CallerID data from modem and drop bogus values instead of crashing. Closes #64 and #78

Modem data for CallerID may contain the following fields:
    DATE := 4..6 digit month and day MMDD[YY] (Verify valid month/day values)
    TIME := 4 digit hour and minute HHMM (Verify valid hour/minute values) 
    NMBR := 4..17 digit phone number (required)
    NAME := [optional] 2..15 letters/spaces. Must start with letter.

Installation as an upgrade will install some new dependencies.