Add istanbul to gulp task test

The tests will fail if less then 75% of the code isn't covered

Closes simcaq/SCRUM#20

Added 1 commit:

• 608e0c1a - Add build status and coverage status badge

Added 1 commit:

• 49c7842b - Change gitlab_ci file to use gulp test task

Added 1 commit:

• e6c24d65 - Add more test cases

Added 1 commit:

• 7250b792 - Set test coverage threshold at 80%

Status changed to merged

Mentioned in commit 6c1963d4