Implement lexima#stack
Implement rules as a sortedlist
Add filetype rules
Fix wrong behavior when the cursor is at the left edge
Add syntax rule
Implement stack.count()
Can leave with count
Always clear the input stack
Refactor leave implementation
Implement leave_till_eol
Be safe when stack.pop count is over the stack count
Add on_change event to charstack
Rewrite tests to vimspec style
Implement commandline rule