Migrate to Android Studio / gradle build system
Remove bundled zxing library in favor of a gradle dependency
Update Android Studio files
Copy token to clipboard automatically on token click

This mimicks the behavior of Google Authenticator and simplifies the UI.

Also, remove the title of the clipboard data so as not leak metadata
about the data in the clipboard. When the title was specified, third
parties could tell that the data in the clipboard was token data.
Because clipboard copying was a manual process, this was not so
problematic. However, now that clipboard copying is on by default,
third parties can snoop this data more easily. So we should at least
avoid broadcasting that the data in the clipboard is a token code.

Fixes #28
Remove button and title from About dialog
Give QR Code Scanning its own menu option
Move add/scan activities off of the DialogActivity model
Make QR code scanning a full screen activity
Move rename/delete activities off of the DialogActivity model
Make the RenameActivity UI smarter
Migrate to gson based token persistence
Add image support
Add support for opening token URIs
Don't be so strict on enforcing base32 key length

Fixes #15
Add support for token image via URI
Remove the redundant issuerlabel file
Rework add dialog to support token image
Migrate to a grid-based UI per the Material Design guidelines
Fix some misc android lint issues
Show token image in deletion confirmation