Fixed issues with code example in README

These changes were made to the wiki home page during the release process
for v1.2.0 but the README was not updated with the same changes.
I have updated the sub-tasks of the cloneable release task to include
a mention to update the README code samples and also moved the sub-task
named 'Update the wiki home page and README' from step 11 to step 7, so
the README will be updated before merging develop into master.
Merge branch 'develop' of https://github.com/ScottLogic/insight into develop
Indentation change after upgrading to grunt-jsbeautifier 0.2.7
Using 'mean' rather than 'Average' for means on Groupings
Removed Grouping.isOrdered()

The private postAggregationCalculations function in Grouping was passing
self.orderingFunction to self.extractData, but only if
Grouping.isOrdered returned true. However, the base
DataProvider.extractData function would still order the data using the
self.orderingFunction, rendering Grouping.isOrdered useless.
Removed Grouping.isOrdered() from tests.
Using lowercase for Grouping sum, count and total calculated properties
Updated documentation for Dimension and Grouping
Reduced the size of the one-to-many Grouping.extractData example
Updated change log
More documentation for Grouping: sum, cumulative, count and mean.
Updated change log
Fixed mistakes in change log
Replaced total with totalCount in result of counting Grouping properties
Merge branch 'develop' of https://github.com/ScottLogic/insight into feature/review-groupings

Conflicts:
	src/mda/Grouping.js
Merge pull request #260 from niksoper/feature/review-groupings

Reviewed support for working with groupings