-Defined lines utility function
-More work on s-expression navigation
-Quasi-working forward and backward sexp movers. Still need to
	- handle strings properly
		- if we start at the beginning of a string, skip over it
		- internally, move by word
		- don't tally parens inside of strings
	- handle comments properly (same stuff as strings, basically)
-See if you can factor out commonalities between the sexp directions
-See if you can factor out the skip-* common points too. We'll need a skip-while and skip-until anyway (taking predicates rather than characters); the rest of them can probably be implemented in terms of those two.