Baby steps #1 in a series: csat/TextOffsetValidator is now CsatTextOffsetChecker.

Cleans an imminent-future naming conflict. This also serves as a reminder of the necessity of Trello Card #26 (https://trello.com/c/y3tMryUC/).

Other problems lurk in the Csat* code, but since it’s explicitly for this feature-exploration demo only, not going to worry about them until/unless it’s unavoidable.

Also added Sugar (http://sugarjs.com/) to the Gemfile, as it brings several important fixes to various jQuery objects that we’ll be making use of imminently.
Baby steps #2 and last in a series: csat/NodeIndexValidator is now CsatNodeIndexChecker.

Cleans an imminent-future naming conflict. As previously noted, other problems lurk in the Csat* code, but since it’s explicitly for this feature-exploration demo only, not going to worry about them until/unless it’s unavoidable.

Also left a note in `welcome.js` reminding that the `createSelection` function needs to be completely rewritten, as it depended on the formerly-used jQuery++ `$.Range` plugin. Yes, that’s a design defect masquerading as a change.