#66 Add sysfs support to battery plugin

[nick]

The battery plugin reads info from /proc/acpi, which is deprecated behavior. This patch adds support for reading from /sys, which is the suggested behavior.

Patch should apply against svn 513.

[nick]

Sysfs battery plugin patch

[nick]

updated patch to check for both energy_now/full and charge_now/full files, as the most recent kernels seem to use the energy file, but older use charge