changing the way logo is sent to travis

[alok760]

I'm submitting a ... (check one with "x")

• [x] bug report
• [ ] feature request
• [ ] support request => Please do not submit support requests here, instead ask your query in out Gitter channel at https://gitter.im/fossasia/meilix

Actual Behaviour The current method of sending the logo to Travis is subject to race around condition.

Expected Behaviour Upload the logo to a server(3rd party service) and send the URL of the logo to Travis. Have the previous method as a fallback.

Related code: https://github.com/fossasia/meilix-generator/blob/02b23dfcd0af51c078d2477ebd29b7c3c4ef0eaa/app.py#L86-L95

Would you like to work on the issue? Yes