Minor documentation fixes.
Fixed a couple of method signatures that did not match the inherited prototype.
Added some missing cases to the calendar unit switch statement. Fixed issue 535.
Added momentum scrolling and "rubber band" snap-back code from Travis Fischer.

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branch : momentumScrolling
Added documentation and private properties for all iVars. Cleaned up the code to conform with Core Plot coding guidelines.

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branch : momentumScrolling
Added utility functions to compute the minimum and maximum of two NSDecimal values.

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branch : momentumScrolling
Fixed an axis rendering issue when the axis has a shadow.
Fixed some plot rendering issues when the plots have a shadow. Fixed issue 533.
Added an absolute value function to the NSDecimal utilities.

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branch : momentumScrolling
Updated the momentum scrolling and elastic plot range code to use CPTAnimation instead of blocks. Added support for the y-range in addition to the x-range.

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branch : momentumScrolling
Updated the Mac CPTTestApp to demonstrate momentum scrolling and elastic plot ranges.

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branch : momentumScrolling
Added property setters in CPTPlotSymbol to force a redraw after changing the appearance properties (line style, fill, clip rule).
Simplified handling of rounded rectangle paths.
Fixed some pixel alignment issues in legends.
Fixed a pixel alignment issue. Fixed issue 541.
Fixed a crashing issue when using attributed strings under iOS 5 and earlier.
Updated the unit tests to match the updated pixel alignment code.
Force plot symbols to redraw when switching between Retina and non-Retina displays.
Merged the momentumScrolling branch into default. Fixed issue 531.
Fixer a bug with elastic plot ranges.