Give users the ability to edit their tables

When they're in "write access" mode, the table visualization now
presents editable cells and a new "Save" button.  Clicking this
will upload the new version of the table back to girder.
Changing behavior slightly

* Removing dependence on table.js needing to know about flow or window.app
* Saving data locally before attempting to save back to Girder
* Changing behavior so if the data is not in a collection, it just saves it locally.
Merge pull request #49 from tangelo-hub/edit_table

I like the changes you made in this latest commit.  LGTM, merging.