HOME is not passed to configparser initialization

[wumb0]

USER is passed in, but HOME is not. This causes the variable replacement in the dockersh.ini to fail with the following error.

configparser.InterpolationMissingOptionError: Bad value substitution: option 'homedir' in section 'DEFAULT' contains an interpolation key 'HOME' which is not a valid option name. Raw value: '${HOME}'

https://github.com/sleeepyjack/dockersh/blob/master/dockersh#L115
Perhaps add HOME: os.environ['HOME'] to the config_envir dict.