Vt-py

* Improve feed iterator implementation to match the iterator protocol (75)

* Raise `TypeError` if the argument passed to `scan_file` is not a file object (https://github.com/VirusTotal/vt-py/pull/70).

* Improve iterator implementation to match the iterator protocol (68)

* Add error handling to 'download_file' (64)

* Add a timeout parameter to the `Client` object (https://github.com/VirusTotal/vt-py/pull/54)
* Fix truncated responses under high load error (https://github.com/VirusTotal/vt-py/pull/56)
* General code improvements (https://github.com/VirusTotal/vt-py/pull/59, https://github.com/VirusTotal/vt-py/pull/60)

* Fix bug that returned None value between batches when iterating over a collection (50)