Updates to website after introduction of DataProvider in library

orderFunction => orderingFunction
getData => extractData
Updated website after visual checks against drawing charts with no data
Updated website after merge in library code

Merged 'allow charts to be drawn with no data' and 'manual axis ranges'
Updated website with docs referring to insight.DataProvider
Updated website after library changes allowing charts to draw without data
Fixed issues found during visual testing

Updated correlation.fromDataSet => correlation.fromDataProvider
Removed vertical tick label orientation from correlation example
Added group name parameter to dataset.group example text
Updated library code after visual testing issues fixed
Merge pull request #246 from niksoper/gh-pages-dev

Updated website after library changes to allow charts to be drawn without data
Updated library code after adding date and version number to change log
Merge pull request #250 from niksoper/gh-pages-dev

Updated library code after adding date and version number to change log