Credit to @johnmellor for requesting the document provider in the
first place via #79, mentioning this limitation in a comment on
that issue, and creating a commit like this one to address it.
As we have a document provider now we can remove ACTION_GET_CONTENT.
"The ACTION_OPEN_DOCUMENT intent is only available on devices running
Android 4.4 and higher. If you want your application to support
ACTION_GET_CONTENT to accommodate devices that are running Android 4.3
and lower, you should disable the ACTION_GET_CONTENT intent filter in
your manifest for devices running Android 4.4 or higher. A document
provider and ACTION_GET_CONTENT should be considered mutually exclusive.
If you support both of them simultaneously, your app will appear twice
in the system picker UI, offering two different ways of accessing your
stored data. This would be confusing for users."
- http://developer.android.com/guide/topics/providers/document-provider.html#43
