This commit will help the user to easily update their existing gist
using zsh auto-completion rather than going to github and then
extracting the required gist hash/URL
Note: This commit effects the working of file: `src/_gist`
Fetches and offers completion for the gists of the currently logged in
user (via gist -l) for the '-r' and '--read' arguments
The data is cached for one day before expiring