Code review comment for lp:~akwm/vm/abbreviate-headers

I think I have addressed all the issues brought up so far in the
updated branch. This includes using vm-match-header (which did not
have the most obvious doc-string, I didn't realize at first that it
matches the header at point and doesn't search...), improvements to
the indicator of shrunken headers using vm-mime-button face and the
">>>/<<<" indicators - though, Uday, I'm not sure what you meant about
it being shorter if the face could be used?, and added some comments
for the fill code along with some changes that make it smaller and
clearer.

Please let me know what you think about the changes. Then the next
thing is to add some info file documentation, I will try and find a
good entry point unless someone already has a good spot in mind.

Thanks,
-Arik