According to the [sysfs class power ABI],
/sys/class/power_supply/<supply_name>/status may contain "Not charging".
This is already handled by status_gt() and update() (where ' ' is
converted to '-' for use in config keys) but was not being read due to
skipws. Read with std::getline() to handle this case.
[sysfs class power ABI]: https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-class-powerFixes: #1139
Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
