Enable code coverage reports #196
Description
Integrate code coverage into the test suite using both simplecov and deep-cover.
The standard coverage in Ruby does not analyzes code branches and misses certain conditionals such as case statements. Integrate the deep-cover gem into the test suite to get more accurate code coverage reports.
When COVERAGE=true is set, the test suite should use simplecov. When COVERAGE=deep is set, the test suite should use deep-cover.