Update to the latest stable release:

• python 3.7 support
• BACKWARD INCOMPATIBLE: Changed signature of DoitCommand
• BACKWARD INCOMPATIBLE: Fix #254: Python actions keywords with task metadata dependencies, targets and changed are a copied list
• BACKWARD INCOMPATIBLE: Custom backend initializer added parameter codec_cls
• Fix #204: Accept loader command options before command name
• Fix #240: Command run: with --pdb drop into pdb on unhandled exception on PythonAction
• Fix #203: Allow configuration of dodo.py file name with env var DOIT_FILE
• Fix #113: tools.config_changed deals with nested dictionaries. Using json instead of repr.
• Fix #261: help organize command options in sections, and improve formatting.
• Fix #267: doit list now has a --sort parameter to determine the order in which the tasks are listed.
• Make it possible to use a custom encoder when using config_changed with a dict.
• Add configuration DOIT_CONFIG action_string_formatting to control command action formatter.
• Fix result_dep, use result after its execution
• Fix #286: Support functools.partial on tasks' dict metadata task.title
• Fix #285: clean command, remove targets in reverse lexical order
• Deprecated TaskLoader in favor of TaskLoader2, which separates loading doit's configuration from loading tasks.
• Fix #288: Added doit.globals.Globals.dep_manager to access dependency manager during all task processing phases.
• Fix #98: Support custom backend codecs so that python-action return values which are not JSON serializable may be used.
• Fix #283: set task options from doit.cfg