Initial attempt at supporting coveralls.io

The following grunt tasks are now available:

 * `grunt test` - Run the unit tests
 * `grunt test-module:oae-telemetry` - Run the unit tests for a specific module (in this case oae-telemetry)
 * `grunt test-coverage` - Run the unit tests and generate a coverage report in `./target/lcov-report/index.html`
 * `grunt test-coverage-coveralls` - Run the unit test and submit the coverage report to coveralls.io
(Issue 735) Move lastModified up to API for discussions and principals
Merge pull request #735 from mrvisser/issue-735

`lastModified` should be managed in API instead of DAO
Merge pull request #742 from simong/coveralls

Initial attempt at supporting coveralls.io