lcov coverage report flag launches browser

[ahmadnassri]

when running tap with --coverage-report=lcov the browser is automatically opened to coverage/lcov-report/index.html.

this seems in conflict with the documentation on the website:

To specify a report format, you can use --coverage-report=. The default type is text, which produces a pretty text-only table on the terminal. If you specify --coverage-report=html, then tap will attempt to open a web browser to view the report after the test run.

[isaacs]

lcov is the same as html. Maybe what you want is lcov-text?

Doc patch welcome.

[ahmadnassri]

@isaacs gave the docs on this a bit of an update to help future readers: #435