Deprecated two methods

lineColorForIndex & lineAlphaForIndex are now deprecated in preparation
of new update.
Update README.md
Bug fix

- Fixed issue #31
- Fixed exception for graph initialized with 0 or 1 points
Feature branch catch up on Master branch + bug fix

- Couldn't automatically merge PR#32. Replicated the modifications from
the master branch to the feature branch.
- Added exception when only one point is given to the data source.