Update Sailor Tests

[hannah-bulmer]

I think there are a few changes it would be smart to make to Sailor's tests before we make any significant updates to Sailor itself (e.g. enhancements, bug fixes, inevitably fixing some of the old tech debts, etc). The details of what should be done and the reason for need are detailed below:

1. Fix the existing broken tests. On master, there is one jasmine test that does not pass, and a few of the mocha tests seem to be failing

2. Migrate existing Jasmine tests to Mocha Chai

• while this might seem like unnecessary work, the benefits of migrating tests from Jasmine to Mocha is that it will make making changes to Sailor safer as it will be EASIER to test and EASIER to see what the tests currently cover and don't cover, and where tests are located for a given function/file
• having both Jasmine and Mocha actively used in unit testing doesn't really make much sense, and it is confusing (and seemingly arbitrary) which framework covers which tests
• converting the Jasmine tests to Mocha/Chai shouldn't take a massive amount of work since both frameworks use fairly similar syntaxes, but will be a matter of removing unneeded packages and changing some of the expect syntax. There is actually a little package here that might help with the converting process

3. Consider migrating our gulpfile to npm scripts

• same reasons as above, mostly. Gulp only really has one task, and it is to run the test-coverage framework Istanbul, which could be done through an npm script

4. Investigate test coverage using Istanbul, make sure all of Sailor is covered by existing tests.