Added title placeholder for the pages screen.

Title has it.

Fixes https://github.com/wordpress-mobile/WordPress-iOS-Editor/issues/373:

![screen shot 2014-11-13 at 12 10 30 pm](https://cloud.githubusercontent.com/assets/154014/5033739/2025f6a8-6b2e-11e4-9ccf-187705806ae1.png)

/cc @diegoreymendez