Various fixes/imporvements to jsnoop.common.archives module
* hasattr checks for properties and cleanup functions replaced with try/catch
* cleanup now correctly called on del of AbstractArchive instances
* cleanup method now made internal
* added comments for is_tarfile and is_archive methods
* made all implementations of AbstractArchive behave similarly for extract/extract_all
* extract_all now has force_file_obj parameter to specify that we want
* file-like-objects instead of file paths when dealing with stuff on-disk
* file_to_bio mehtod added to convert files on disk to BIO
* fileobjects created from ondisk directories now give empty BIO object for sanity
* native archives now correctly return list of filepaths/file-like-objects
Merge branch 'master' of github.com:abn/jsnoop