Update codecov to 2.1.0

[pyup-bot]

This PR updates codecov from 2.0.11 to 2.1.0.

Changelog

### 2.0.21 ``` - fixed string issues ``` ### 2.0.20 ``` - fixed broken subprocess handling ``` ### 2.0.19 ``` - fixed broken subprocess handling ``` ### 2.0.18 ``` - fixed broken subprocess handling ``` ### 2.0.17 ``` - fixed reported command injection vulnerability. ``` ### 2.0.16 ``` - fixed reported command injection vulnerability. ``` ### 2.0.15 ``` - add `-X s3` to disable direct to S3 uploading ``` ### 2.0.14 ``` - fixed coverage combine ``` ### 2.0.13 ``` - fix encoding issues ``` ### 2.0.12 ``` - revert merge commit fix, back to old way ```

Links

- PyPI: https://pypi.org/project/codecov - Changelog: https://pyup.io/changelogs/codecov/ - Repo: https://github.com/codecov/codecov-python

[pyup-bot]

Closing this in favor of #21