Removed reading the temperature data from sysfs. lm_sensors handles this better.
Removed unnecessary local variables.
Replaced for with for each where applicable.
Refactored panel output.
Replaced Preferences Button with real ellipsis.
Refactored sensors and hddtemp parsing.
Replaced synchronous API with asynchronous API to call of sensors and hddtemp.

Closes #16
Added reaping of child processes.