Set closed-source score to blockchain.info

Updated source code for the Android wallet isn't available. There is strangly only a single "Initial commit" since 21 days, so Android users are using updated versions based on unpublished code.

https://github.com/blockchain/My-Wallet-Android

@zootreeves Please feel free to comment or fix the issue.

In the absence of critical feedback, this pull request will be merged on August 11th.