Some pageNav links don't work, possibly due to the use of colon

[damithc]

Steps:

1. Go to https://nus-cs2113-ay1920s2.github.io/website/admin/tp-deliverables.html
2. Click on one of these links
   

Problem: the page doesn't scroll to the relevant heading. No such problem with the other links in the PageNav. Is it something to do with the use of : in the heading?

[ang-zeyu]

The headings inside the Practical Exam that will be done at v2.1 modal are getting indexed, will get a fix out