Fixed http request not being aborted

[pasin]

Currently we are using fetch polyfill which has abort feature pending as a result we couldn't really abort http requests. Fake aborting has been implemented but this doesn't well with Channels page that send longpoll requests.

We could fix this by using other http client libraries:

• Superagent
• axios (from https://github.com/msangui/axios fork)
• XHR

[pasin]

Personally I prefer the axios library over the superagent as its API is very similar to the fetch polyfill. However they have the same issue with fetch polyfill as there is no standard way to cancel the promise. They are currently working on the solution. Once either axios or fetch polyfill has the abort feature implemented, we could just switch to use the library. Meanwhile I will keep this issue open.