Backport changes from (true) wiki to source in git repository

* Colro -> Color
*  dc.units["float"] -> dc.units.fp

Maybe there should be a warning that the page is maintained via the git repository ?
Bug #282
We initialize `_dataLayers` up front

If there is no data, then `initializeDataLayer` is never called and
_dataLayers is never initialised properly leading to the bug
manifesting in #284. We initialise _dataLayers to `[[ ]]` up front.
Closes #284.
Merge #285
Fix the jsfiddle issue in #284 with null d
update web task in Grunt
Merge pull request #281 from BertrandDechoux/patch-2

Backport changes from (true) wiki to source in git repository
Update README.md
fix #229
fixes spelling in css strok -> stroke
fix #214
Merge pull request #288 from stevemartingale/spellingcss

fixes spelling in css strok -> stroke
fix #233 - support drawArea
Extra fake unit not needed in ordinal bar chart after #229
Add axis labels. Closes #271
add axis labels to stock example
Fixes #244
Add Number Chart

Fixes #6
some small cleanup of crime example
redo number chart