fixed some layout issues, added Date XAxis, cleaned up, added comments

README.md

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

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

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

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

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

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

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

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

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

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

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

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

src/main/java/com/xeiam/xchart/interfaces/IHideable.java

src/main/java/com/xeiam/xchart/series/Series.java

src/main/java/com/xeiam/xchart/swing/SwingWrapper.java

src/main/java/com/xeiam/xchart/swing/XChartJPanel.java

src/test/java/com/xeiam/xchart/example/Example10.java

src/test/java/com/xeiam/xchart/example/Example3.java

src/test/java/com/xeiam/xchart/example/Example9.java