Add 'no comments' message to SPV

In the SPV we have a completely white right side if there are no comments and no other interactions. Here is how it will look like when merging this PR:
![no_comments_spv](https://f.cloud.github.com/assets/3798614/1013340/0f4c93e6-0b85-11e3-9061-d7119551a4a1.png)