Test coverage

[thwllms]

Closes #36

• Adds pytest-cov as an optional dependency
• Runs test coverage reports as part of CI process
• Uploads test coverage reports to Codecov

Reviewing

• Install updated depenencies: pip install ".[dev]"
• Run unit tests with coverage: pytest --cov rashdf
• Generate a coverage report: pytest --cov rashdf --cov-report html (open the HTML files in the htmlcov directory to view test coverage reports)
• Check out coverage report generated for this PR on Codecov (red highlighted sections are lines not covered by unit tests): https://app.codecov.io/github/fema-ffrd/rashdf/pull/41/blob/src/rashdf/utils.py

[codecov[bot]]

Welcome to Codecov :tada:

Once you merge this PR into your default branch, you're all set! Codecov will compare coverage reports and display results in all future pull requests.

:information_source: You can also turn on project coverage checks and project coverage reporting on Pull Request comment

Thanks for integrating Codecov - We've got you covered :open_umbrella: