Wallet model and testing

Wallet.js with the following methods:

* getBalance: return balance in btc (receive array of utxo)
* listUnspent: return array of unspent outputs (from insight-api). It could be used for getBalance.
* sendRawTransaction: make a POST to insight-api with transaction in hex.

Update:

* Merged with last version on 'master'.
* Test in browser work 100%.
* Fixed path to file copayBundle.js on index files for home and test pages.

Note:

* Not sent copayBundle.js file for avoid conflict. You have to update it with: grunt --target=dev

Conclusion: now it is safe to merge with 'master'.