Version 1.5.9

Changes:

• increase maximum target phone number length to 23, to allow for 5 digit extensions
  this requires a database migration, run with flask migrate up

Updates:

• MarkupSafe to 2.0
• rq to 1.8.1
• redis to 3.5.3
• httplib2 to 0.19.0
• Flask-Cors to 3.0.9