use `a:count` instead of `count` in a function

Note: note sure why it worked before and how it works.
map "S to yank a trimmed line
Last Change: 2014-06-22
document 'S mapping
fix a typo in a comment
format comments
use XXX instead of NOTE to signal dependencies
use my customized version of "matchit" plugin
Last Change: 2014-06-28