Cache contribution images

[maskaravivek]

Summary:

It seems the images displayed in the contribution list isn't getting cached properly.

Steps to reproduce:

• Load contribution list
• Kill the app
• Switch off the internet
• Open the app again

Commons app version:

latest master.

Screen-shots:

Would you like to work on the issue?

Yes

[nicolas-raoul]

@maskaravivek I see you are assigned to this issue, would you mind sharing what is the status? Thanks :-)