Remove dead code: accessing curpos

curpos is a side-effect free attr_reader. Should be safe to remove
Use _ to ignore unused splats
Remove warnings about variable shadowing
Make chronic a hard dependency

The chronic gem is pure Ruby, works on from 1.8.7 to 2.0.0 and only 39k in
size. No reason not to install it by default.
Remove doc/NewUserGuide.txt since it's in the wiki now.
Replace dash with underscore in filename