added ticker marks below and above min and max values if with a certain tolerance.

...n/java/com/xeiam/xchart/demo/charts/date/DateChart03.java

.../com/xeiam/xchart/demo/charts/scatter/ScatterChart02.java

xchart/src/main/java/com/xeiam/xchart/Histogram.java

...m/xeiam/xchart/internal/chartpart/AxisTickCalculator.java

...iam/xchart/internal/chartpart/AxisTickDateCalculator.java

...art/internal/chartpart/AxisTickLogarithmicCalculator.java

...chart/internal/chartpart/AxisTickNumericalCalculator.java