Add podspec file to enable TICoreDataSync to work with cocoapods

Once fully integrated, users will be able to include TICoreDataSync by adding this line to their Podfile:

pod 'TICoreDataSync'

For now, there are a few caveats:

1. It's on the develop branch rather than master. The reason for this is that it requires version 1.3.3 of
the Dropbox SDK.

2. It installs the :head version of TICDS. This makes sense during development but a better practice is
to add version tags to the master branch and then have the podspec reference particular versions.

3. It's not yet in the cocoapods specs repo. This should occur once the podspec is merged to the master
branch and a particular tag referenced.

To try it out, create a Podfile like this:

platform :ios, '6.0'

pod 'TICoreDataSync', :podspec => "path/to/TICoreDataSync.podspec"
Merge pull request #33 from dhennessy/develop

Add podspec file to enable TICoreDataSync to work with cocoapods