Replace ',' on '.' in cpu and mem. Fix #6

In my system command 'ps' returns strings in format "0,0  1,6 com.apple.WebKit.WebContent". 
Function "parseFloat(stats[stat].cpu / os.cpus().length);" returns NaN when 'cpu' has ',' in float, and returns correct answer with '.'.
Merge pull request #9 from isalem/patch-1

Replace ',' on '.' in cpu and mem. Fix #6