Fix test suite

[rovolution]

Unit test suite is not working locally as reported here - https://github.com/seiyria/bootstrap-
slider/pull/692#issuecomment-273859884

I ran this locally and confirmed the bug.

I will look into this when I get a chance.

[futhr]

I got stuck here:

grunt build
(node:13793) DeprecationWarning: os.tmpDir() is deprecated. Use os.tmpdir() instead.
Running "less:development" (less) task
File temp/bootstrap-slider.css created.

Running "babel:dist" (babel) task

Running "less:development" (less) task
File temp/bootstrap-slider.css created.

Running "jasmine:src" (jasmine) task
Testing jasmine specs via phantom

Running PhantomJS...ERROR
>> 0 [ '' ]
Warning: PhantomJS exited unexpectedly with exit code null. Use --force to continue.

[rovolution]

Unit test suite is up and running again!