Removed travis config to stop using travis for CI

[mraarif]

No description provided.

[mraarif]

@jmbowman coverage report was uploaded to codecov.io (https://codecov.io/gh/edx/edx-drf-extensions) when it ran against this PR, do we need to update codecov check here? it seems to be unable to locate the coverage report since we removed travis.yml

[jmbowman]

@mraarif I just did some hunting around, and it seems like this is a known bug in the checkout@v2 action (which GitHub thinks they fixed, but people are still hitting):

• https://community.codecov.io/t/codecov-status-stuck-at-waiting-for-status-to-be-reported-on-github/341/45
• on pull request, checkout@v2 built some ref other than the one that was claimed actions/checkout#237
• Checking out wrong commit? actions/checkout#299

Using v1 of the checkout action seemed to work for most people, maybe just try that? There's another suggested fix at actions/checkout#299 (comment) , but I don't see confirmation that it's working for others.

[mraarif]

@jmbowman using actions/checkout@v1 seems to have fixed the issue, thanks