Towards Unified Editing

[sameersingh]

Meta issue to track all the issues for unified fluid editing.

Multiple features to create the next generation of unified editing:

• [x] All ACE editing, #48
• [x] cursors moves fluidly between cells, done.
• [x] change modes using keyboard, done: #50
• [x] Split/Merge/Delete: currently only delete supported, #52
• [ ] Allow line numbers to continue? Might not be important or easy
• [x] Layout and formatting.

[sameersingh]

This seems pretty much done.