Update README.md
Merge pull request #14 from prashantbhat/master

Moved localization bundle properties to src/main/resources folder
Reuse Color objects in GrayPaintScale, plus tightened up parameter checking for PaintScale methods.
Fixed typo in comments.
Replace tabs with spaces.
Replace tabs with spaces.
Replace tabs with spaces.
Replace tabs with spaces.
Add getAnnotations() method to XYItemRenderer interface.