Basic search implementation.
Search doesn't always start on the current line.
Search for nth match.
Extract a method to search & move.
Repeat searches with n and N.
Add search commands to README.
Search should wrap to start/end of document.
Backward search.
Improve descriptions of search commands.
Add backward search to the README.
Split Operation.keyPress into shorter methods.
Command line args are just args now.

Breaks command line rendering, but makes the code much nicer.
Use search commands as motions.
Rename NullArgument to NoArgument.
More robust moveCursor method.

* Ignore null or undefined values.
* Accept an object with row and col properties.
Refactor moveToNext and moveToLast.

Rather than explicitly handling null results, findNext and findLast now
return a useful object whether they find what we wanted or not.
Use the more flexible moveCursor interface.