Read both {energy,charge}_now and {energy,charge}_full to determine battery status

lifebar uses the following files to determine the battery status: 
  - `/sys/class/power_supply/BAT0/energy_full`
  - `/sys/class/power_supply/BAT0/energy_new` 

According to [this thread](http://comments.gmane.org/gmane.linux.acpi.devel/51602) on the Linux ACPI Development Discussion List there are probably other files available under certain circumstances: 
  - `/sys/class/power_supply/BAT0/charge_full`
  - `/sys/class/power_supply/BAT0/charge_new` 

This pull request now covers both `energy_*` and `charge_*` files.
What do you think?