added missing license header
Merge pull request #49 from leonard-dev/master

added missing license header
Added TestLogScale and LogScale 

Signed-off-by: anthoni <schiochetanthoni@gmail.com>
commented Test LogScale.tickFormat

Signed-off-by: anthoni <schiochetanthoni@gmail.com>
Added PowScale and TestPowScale

Signed-off-by: anthoni <schiochetanthoni@gmail.com>
Merge with upstream