Gather code coverage

[Parowicz]

Welcome to Dart community

@cclauss i've fixed your pull request according to #100
Right now I'm saving coverage in *.lcov format. You have ideas how to proceed?

Describe your change:

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Dart files are placed inside an existing directory.
• All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

[cclauss]

LOL!! --pretty-print spits out way too much information!! I was just looking for a percent of test coverage for each file.

• a.dart 20%
• b.dart 90%
• c.dart 0%

[Parowicz]

@cclauss lcov -l coverage.lcov format will do?

[cclauss]

Does this mean that every dart file has tests and there are no dart files that have 0% code coverage?

[Parowicz]

dart test executor is executing all main function and when examples run they mostly cover whole file.
For real test coverage we would need to put all tests in separate directory - now it's test coverage + examples coverage.

[cclauss]

Cool. I think this is good to go.