Update code-base to parse "BestFitSequence"

- Update code-base to parse new sequence "BestFitSequence".

- Add color override for "data-defs" in the expanded JSON.

- Modify legend block in the expanded JSON to support more types.

- Add type "AvgSumOfDeviation" in legend for "BestFitSequence".
Add "BestFitSequence" code files

- Add "BestFitSequence" code files.
Update "runtimeSchema.json" and sample files

- Update "runtimeSchema.json" and sample files as per the new format
  for legend data in the expanded JSON.
Add sample files for "BestFitSequence"

- Add sample files for "BestFitSequence".
Fix bugs for BestFitSequence

- Fix calculation for y-intercept.

- Add 'datarefs' in 'correct_answer' and 'attempts_over' step.

- Fix naming of correct line's datadef.

- Update sample file for BestFitSequence.
Fix 'maxAttempts' bug for BestFitSequence

- Fix 'maxAttempts' bug for values '0' and '1'.

- Add 1 as default 'maxAttempts'.
Update in calculations for BestFitSequence

- Update calculations for slope and y-intercept of best-fit line.

- Update calculations for deviation value of best-fit line from the
  scatter-plot.

- Update title of the legend for BestFitSequence.
Update calculation of deviation value

- Update calculation of deviation value by taking square root of it.
Update sample JSON files for 'BestFitSequence'

- Update sample JSON files for 'BestFitSequence'.
Modify calculation for deviation

- Use sum of squares for calculation of deviation value.
Update output JSON files for 'BestFitSequence'

- Update output JSON file for 'BestFitSequence'.
Refactor and cleanup code for BestFitSequence

- Refactor and cleanup code for BestFitSequence.
Merge pull request #4 from zeuslearning/zeus_rebase_12_11_12_a

Integrate Zeus' line of best-fit.
rm Javascript files in src/
input format for some label features
slope tool: use preferred pattern for adding pane
Merge from 'CC/master'

- Merge from 'CC/master' branch into 'zeus/master' branch.