Update codecov to 2.1.3

[pyup-bot]

This PR updates codecov from 2.0.15 to 2.1.3.

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.

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 #153