Enables SSL in the link tag for the prev and next page

Fixes #4266

Enables SSL in the prev / next links in the head.

Tested on a vagrant machine:

![screen shot 2014-10-13 at 15 07 57](https://cloud.githubusercontent.com/assets/2955483/4614686/af1194b2-52e2-11e4-9b56-b53f89e3658a.png)
![screen shot 2014-10-13 at 15 07 21](https://cloud.githubusercontent.com/assets/2955483/4614687/af12940c-52e2-11e4-86d7-949784b61d57.png)

You're right.