initial version of TwoColorAreaSeries
Code and comments cleanup
Added three examples in example library with two-color area series
code and comments cleanup, proper comments according to warnings from StyleCop
Updated PCL, NET35 and SL4 csproj files.
reject changes with TargetFrameworkVersion in SL4 csproj file
Updated PCL, NET35, SL4 csproj ExampleLibrary files
update CONTRIBUTORS list
Merge pull request #299 from piotrwarzocha/feature-two-colorAreaSeries

Feature two color area series