Add logic for dynamically injecting markup into header.

Make title and file search box configurable (visible by default).

#### Default
![all](https://cloud.githubusercontent.com/assets/96776/4638653/78021e80-53fd-11e4-8ea3-3bae7dc6890e.png)

#### All configured to be hidden
![none](https://cloud.githubusercontent.com/assets/96776/4638657/7a7129cc-53fd-11e4-959a-ac7c92daedaa.png)

#### Title only
![title-only](https://cloud.githubusercontent.com/assets/96776/4638655/7a4a3e5c-53fd-11e4-9d28-aadb974bfc8d.png)

#### Search only
![search-only](https://cloud.githubusercontent.com/assets/96776/4638658/7a73079c-53fd-11e4-9327-e8a544a28539.png)
Can we add a comment in here to document what's going on?