Initialize
Separate update and download command

-u updates all feeds while -d downloads all new episodes.
print usage when user didn't specify an operation
unfuck feed store
cleanup main function
Fixed command line flag processing

It is now possible to invoke multiple stuff at once.

Example:

cpod -i podcasts.opml -u

The above example will import the opml file podcasts.opml and after this
action is completed cpod will immediately update all feeds.
Actually update the feeds when running cpod -u
support more date formats