On Linux calculate battery stats only if battery data available
Merge pull request #4 from tjormola/master

Fix perl warnings when running with defaults on Linux on a machine with no battery
started load/usage separation
MAJOR: using CPU utilization instead of load average by default
documentation update to reflect switch from loadavg to CPU usage
updated screenshots
version bump
Do print two spaces if no battery is available

This ensures a constant length of the output, which is nice if the output is right-aligned, and you have several tmux instances nested from different machines (some with battery, some without).
Add history option for location of history file
Add option to average multiple measures per bar

Useful if the refresh rate is large.
Implement better mapping from values to ticks
Add option to specify custom colors
Don't wait one second after querying top
Show newest measure on right-most bar (no avg)