Adding vim-style counts to commands

[dsanson]

Okay. Here is a pull request to add vim-style count commands, as discussed in issue #5. It enables counts for:

Scroll down Scroll up Page down Page up Next chapter Prev chapter Shrink Enlarge

It also enables counts for the movement commands when viewing the table of contents.

I made some changes to your key bindings:

• I changed the enlarge keybinding to + instead of =
• =, when used with a count, sets the width to that count: e.g., 75= sets the width to 75 columns.
• =, when used without a count, toggles between 80 columns and full width, and so replaces your togglewidth keybinding of 0 (as introduced in response to Issue #9.)
• the Page/Scroll shortcuts now work the same when viewing the table of contents, and both take counts.

[dsanson]

I should say: the [count] movements make no attempt to extend beyond each chapter: if you are on the second to last page of a chapter, for example, and you do 20<space>, it goes to the last page of the chapter, rather than 18 pages into the next chapter.

[wustho]

whoaa, sorry just read this...

Thanks for making it before the end of the year! I actually tried to implement your advice on making vim counter movement, but didn't work out well since I made the basic movement to complicated...

Cool, let me try it first...

[wustho]

woww [counter]set width works seamlessly, thanks for this dsansonn, really appreciate it