Added options for loading and saving catalog data locally, as the 4chan API can be very slow
at times, sometimes taking up to 10 seconds to respond.

4grep g --dump file  => Fetches all threads from /g/ and writes JSON data to ./file
4grep g --dump -     => Writes the JSON data to standard output

4grep --load file => Gets the JSON data from ./file instead of the 4chan API
4grep --load -    => Reads the JSON data from standard input

Note: --load is a boolean switch and does not take an argument. It only tells the script to interpret
the board name as a file path.