Add CocoaPods podspec

CocoaPods podspec for QSKit. 

In order for the podspec to work, you'll need to create a '**v0.0.1**' tag in the repo (or chose your preferred version number and update the `s.version` and `s.source` tags). Pods work best if projects follow [semantic versioning](http://guides.cocoapods.org/making/making-a-cocoapod.html#library-versioning) as APIs are revised...

Users of QSKit can install by adding the following lines to their Podfile:

```
pod 'QSKit', :git => 'https://github.com/quartermaster/QSKit.git'
pod 'QSKit/SQLite', :git => 'https://github.com/quartermaster/QSKit.git'
```
And then running `pod install` in their project directory.