iOS 7 styling, uses the UINavigationBar at the top, cleaned up bar buttons, Cocoapods installation

Hi all,

Decided to fork this project and do some necessary refactoring.

Here's the change list (from the new readme):

* Optimised UI for iOS 7 style.
* Implemented fast pagination as per [this pull request](https://github.com/vfr/Reader/pull/48).
* Ditched the ReaderMainToolbar for the top toolbar. The viewer now uses the current UINavigationController's nav bar. **Note: this means the the viewer is required to be shown in a UINavigationController instance. See README for info.** 
* Ditched cluttered bar button items in favour of two UIBarButtonItems.
* Added ability to open PDF in other apps.
* Moved all framework files into dedicated folder (ReaderFramework).
* Moved assets into Reader.bundle file in /ReaderFramework.
* Added UIPopover approach for iPad actions (see [here](http://imgur.com/rg25feZ)).
* Installation via Cocoapods.