tqdm v4.50.0 stable

• add bar colour option (#1040 <- #450)
  • for notebook as well as std/CLI
  • plain text as well as hex (e.g. 'green' or '#00ff00')
• notebook improvements (#1032 <- #1031)
  • split bar description into separate widget
  • improve reset() (handle width and colour)
• fix exceptions when file is closed (#1041, #1036 <- #1033)
• add & update tests
• minor documentation updates
• move and configure issue/pr templates