Small Pod tweaks.

This is a bunch of Pod tweaks.  I won't be offended if you don't merge.  Essentially the main problem I wanted to fix was the gaps in the source view:  https://metacpan.org/source/KENTNL/HTTP-Tiny-Mech-1.001000/lib/HTTP/Tiny/Mech.pm

I think that's because of the missing `=pod` markers.  As I was changing that I got a Pod error about encoding, so I added the utf8 encoding, which doesn't appear to break anything.

Then I got an error about =attr not being valid, so I changed that to an `=over` and `=item`, which may or may not be in line with the display you were going for.  ;)