Patch for uploads via Travis CI

We recently found an issue regarding uploading coverage reports from Travis CI where users have been able to upload coverage reports for repositories without a Codecov upload token.

We have since patched our systems to prevent tokenless uploads from Travis CI. You may notice that uploading to Codecov will now fail without the proper token.

Additionally, this is not a breach; no code or configurations could be read or changed by an outside party as a result of this issue. We want to make sure you’re back on track as quickly as possible, and you can find documentation on upload tokens here.

This is the solution.