allows to have range_cutoff > range_max

NOTE this is required if we need to keep the range_max readings
in the point cloud.
An example application is an obstacle_layer in a costmap.
updates range_cutoff API documentation
removes trailing white spaces and empty lines
Merge pull request #9 from efernandez/allow_cutoff_higher_than_range_max

allows to have range_cutoff > range_max