Test to make sure arc file header is written just once.

And it is failing now.
Fixed the issue of writing duplicate file header in arc file.
ARCFile: filename is specified should be used and should work even if filename is not specified.
bump version to 0.2.1
Added some bugfixes

Manual addition of some bugfixes found in upstream issues and pull
requests.
Ran 2to3, fixed CaseInsensitiveDict

Almost certainly broken.
Update for python3

Numerous small changes. Update for python3, attempt to remove gzip2 and
use standard library instead. Began creating small tool for HTTP
parsing. Probobly utterly broken.