Add gitignore file
Add contents iteration to the archive

Make the iteration possible on Archive objects. It returns each of the
files from the archive. Name or header details can be retrieved from
attribute .header(.name)
Add tests for iteration
Merge branch 'feature/iteration'
Allow operations on not seekable objects

Make sure that not seekable objects can be used with this library.
Implement reading to a position as a seek replacement and fail on
seeking backwards.
Remove unnecessary check

Seeking to negative offsets is already a ValueError. On nonseekable
streams seek() itself will fail too.
This brings back 100% coverage.
Add tests for the stream scenarios
Add seekability detection

Detect whether the underlaying storage is seekable in order to speed
up skipping over large files. In case of non-seekable streams, arpy
still reverts to reading.
Merge branch 'feature/streams'
Add readme file