v0.5.0

• Automatically redraw the chart when changing series (#25 by @duemunk): no need to call setNeedsDisplay when changing chart's series property
• Update chart on resize (#24 by @duemunk)
• Add xLabelsOrientation option to switch the x-labels orientation between horizontal or vertical (#61)
• Add xLabelsSkipLast option. Set it to false to print the last x-label (the last labe; may overflow the frame size, tough) (#37)