Clean up file to adhere to the PEP8 style guide.

Clean up file using the pep8 library (through the help of SublimeLinter):
- Changed tabs to spaces.
- Added 2 blank lines before classes.
- Removed extra spaces/blank lines.
Prefix the filename with a sequence number.

Prefix the filename with the position of the image in the album.  This gives the user
the ability to sort the images by its original ordering in the imgur album.
Merge pull request #2 from lemuelf/ordered_files

Ordered files
Remove 'http:' in `src` attr of `img` tag.

Imgur removed the 'http:' in the `src` attributes of the `img` tags in
albums so it's now "protocol relative", and use the protocol used in
the request.  This broke `imguralbum.py`, though.

This commit removes the 'http:' in the `findall` matcher of album
images and adds it when downloading the images, and makes
`imguralbum.py` work again.
Add support for https.

Adds the https protocol to the imgur url validator, and also downloads
images using https if the album url parameter uses https.
Merge pull request #4 from lemuelf/protocol_relative

Protocol relative and HTTPS support