• introduced: Environment values FORCE_COLOR_, CLICOLOR_FORCE_, and NO_COLOR_ overrides
  :class:blessed.Terminal argument value, force_styling #295
• improved: performance of :meth:~Terminal.rgb_downconvert for 256-color
  terminals, #298
• deprecated: Python 2.7 through 3.6 no longer supported. #299
• improved: keyboard support for modifier keys, #306
• introduced: kitty keyboard protocol support, #309
• introduced: mouse support, Synchronized Output, and support for DEC Private Modes, #310
• introduced: methods to determine Sixel, dimensions and color depth #312
• introduced: in-band resize support (DEC Private Mode 2048) #313
• introduced: XTVersion identification: #314
• bugfix: default timeout for get_bgcolor, get_fgcolor #315