Allows to open the firefox cookie database even though Firefox is
holding a lock.
Fixes the "Cookie import failed: database is locked" message when using
the script while Firefox was running.
This has been reported in #877.
Such as for downloading hashtag feeds, as discussed in #666 and contributed by
@e2tovar.
Also change comment color to grey in codesnippets in documentation.
Presents code examples that use the instaloader module for more advanced tasks
than what is possible with the Instaloader command line interface.
Presents #46, #56, #110, #113, #120, #121.
